zen trace analysis support (#945)

Integrates the **tourist** trace analysis library and builds a full `zen trace` command suite for working with Unreal Engine `.utrace` files.

### Trace analysis library (`thirdparty/tourist/`)
- Adds the tourist library as a third-party dependency with three modules: **foundation** (platform primitives, memory, scheduling), **trace** (UE Trace protocol decoding), and **analysis** (event dispatching and analyzer framework).
- Cross-platform support for Windows, Linux, and macOS.

### `zen trace` CLI commands (`src/zen/cmds/`, `src/zen/trace/`)
- **`zen trace analyze`** — Summarize a `.utrace` file: session metadata, thread inventory, command line + build configuration, CPU profiling scopes, timing, event rates, log messages, and (with symbols) memory allocation metrics including live-allocs dumps, callstack-keyed aggregation, and allocation churn. Optional HTML output for memory reports.
- **`zen trace inspect`** — Dump the event schema (declared types, fields, sizes) from a trace file.
- **`zen trace trim`** — Extract a time-window from a trace into a new `.utrace` file.
- **`zen trace serve`** — Launch a local HTTP server hosting an interactive trace viewer; opens in the default browser.

### Symbolication (`src/zen/trace/symbol_resolver.*`, `thirdparty/raw_pdb/`)
- Pluggable resolver with multiple backends: `pdb` (in-tree raw_pdb), `dbghelp` (Windows), `llvm-symbolizer` (all platforms), `atos` (macOS). An `auto` backend picks the best available tool per platform.
- Microsoft Symbol Server support: downloads PDBs on demand using a redirect-aware HTTP client.
- Local PDB cache keyed by image GUID preserves symbols across binary recompilation.
- Callstack trimming heuristic strips UE internal noise from reports.
- Binary analysis cache (`.ucache_z`) avoids re-resolving the same trace.

### Interactive trace viewer (`src/zen/frontend/html/`, `src/zen/trace/trace_viewer_service.*`)
- Timeline: scope-level detail, horizontal zoom/pan, vertical scrolling, viewport-driven loading with pre-computed LOD for responsive navigation of large traces.
- Thread grouping (collapsible sidebar sections) synthesized from name suffixes, natural sort order, visual distinction between lane threads and OS threads.
- Bookmark and region annotations; region categories with per-category toggles; bookmark marker toggle in the toolbar.
- Filterable Logs tab showing captured `UE_LOG` output.
- Stats tab with per-scope aggregate statistics.
- Memory tab with interactive allocation analysis and an allocation size histogram.
- CsvProfiler event parsing and chart UI.

### Other in-branch supporting changes
- **Cross-platform browser launcher** (`browser_launcher.{h,cpp}`) used by `trace serve`.
- **`ReciprocalU64`** fast 64-bit integer division (zencore/intmath) for trace analyzers.
- **`parallelsort`** cross-platform parallel sort helper (zenutil).
- Frontend zip build rule so the viewer's HTML assets are bundled into `zen.exe`.
- `/Zo` flag for better optimized debug info on Windows release builds.
- `trace-tests.cpp` in the `zen-test` harness (harness itself landed on main via #985).

1 files changed, 268 insertions, 0 deletions

diff --git a/thirdparty/raw_pdb/src/Examples/ExampleLines.cpp b/thirdparty/raw_pdb/src/Examples/ExampleLines.cpp
new file mode 100644
index 000000000..f055b98c5
--- /dev/null
+++ b/thirdparty/raw_pdb/src/Examples/ExampleLines.cpp
@@ -0,0 +1,268 @@
+// Copyright 2011-2022, Molecular Matters GmbH <[email protected]>
+// See LICENSE.txt for licensing details (2-clause BSD License: https://opensource.org/licenses/BSD-2-Clause)
+
+#include "Examples_PCH.h"
+#include "ExampleTimedScope.h"
+#include "Foundation/PDB_PointerUtil.h"
+#include "PDB_RawFile.h"
+#include "PDB_DBIStream.h"
+#include "PDB_InfoStream.h"
+
+#include <cstring>
+
+namespace
+{
+	struct Section
+	{
+		uint16_t index;
+		uint32_t offset;
+		size_t   lineIndex;
+	};
+
+	struct Filename
+	{
+		uint32_t fileChecksumOffset;
+		uint32_t namesFilenameOffset;
+		PDB::CodeView::DBI::ChecksumKind checksumKind;
+		uint8_t  checksumSize;
+		uint8_t  checksum[32];
+	};
+
+	struct Line
+	{
+		uint32_t lineNumber;
+		uint32_t codeSize;
+		size_t   filenameIndex;
+	};
+}
+
+void ExampleLines(const PDB::RawFile& rawPdbFile, const PDB::DBIStream& dbiStream, const PDB::InfoStream& infoStream);
+void ExampleLines(const PDB::RawFile& rawPdbFile, const PDB::DBIStream& dbiStream, const PDB::InfoStream& infoStream)
+{
+	if (!infoStream.HasNamesStream())
+	{
+		printf("PDB has no '/names' stream for looking up filenames for lines, skipping \"Lines\" example.");
+		return;
+	}
+
+	TimedScope total("\nRunning example \"Lines\"");
+
+	// prepare the image section stream first. it is needed for converting section + offset into an RVA
+	TimedScope sectionScope("Reading image section stream");
+	const PDB::ImageSectionStream imageSectionStream = dbiStream.CreateImageSectionStream(rawPdbFile);
+	sectionScope.Done();
+
+	// prepare the module info stream for grabbing function symbols from modules
+	TimedScope moduleScope("Reading module info stream");
+	const PDB::ModuleInfoStream moduleInfoStream = dbiStream.CreateModuleInfoStream(rawPdbFile);
+	moduleScope.Done();
+
+	// prepare names stream for grabbing file paths from lines
+	TimedScope namesScope("Reading names stream");
+	const PDB::NamesStream namesStream = infoStream.CreateNamesStream(rawPdbFile);
+	namesScope.Done();
+
+	// keeping sections and lines separate, as sorting the smaller Section struct is 2x faster in release builds
+	// than having all the fields in one big Line struct and sorting those.
+	std::vector<Section> sections;
+	std::vector<Filename> filenames;
+	std::vector<Line> lines;
+
+	{
+		TimedScope scope("Storing lines from modules");
+
+		const PDB::ArrayView<PDB::ModuleInfoStream::Module> modules = moduleInfoStream.GetModules();
+
+		for (const PDB::ModuleInfoStream::Module& module : modules)
+		{
+			if (!module.HasLineStream())
+			{
+				continue;
+			}
+
+			const PDB::ModuleLineStream moduleLineStream = module.CreateLineStream(rawPdbFile);
+
+			const size_t moduleFilenamesStartIndex = filenames.size();
+			const PDB::CodeView::DBI::FileChecksumHeader* moduleFileChecksumHeader = nullptr;
+
+			moduleLineStream.ForEachSection([&moduleLineStream, &namesStream, &moduleFileChecksumHeader, &sections, &filenames, &lines](const PDB::CodeView::DBI::LineSection* lineSection)
+			{
+				if (lineSection->header.kind == PDB::CodeView::DBI::DebugSubsectionKind::S_LINES)
+				{
+					moduleLineStream.ForEachLinesBlock(lineSection, 
+					[&lineSection, &sections, &filenames, &lines](const PDB::CodeView::DBI::LinesFileBlockHeader* linesBlockHeader, const PDB::CodeView::DBI::Line* blocklines, const PDB::CodeView::DBI::Column* blockColumns)
+					{
+						if (linesBlockHeader->numLines == 0)
+						{
+							return;
+						}
+
+						const PDB::CodeView::DBI::Line& firstLine = blocklines[0];
+
+						const uint16_t sectionIndex  = lineSection->linesHeader.sectionIndex;
+						const uint32_t sectionOffset = lineSection->linesHeader.sectionOffset;
+						const uint32_t fileChecksumOffset = linesBlockHeader->fileChecksumOffset;
+
+						const size_t filenameIndex = filenames.size();
+
+						// there will be duplicate filenames for any real world pdb. 
+						// ideally the filenames would be stored in a map with the filename or checksum as the key.
+						// but that would complicate the logic in this example and therefore just use a vector to make it easier to understand.
+						filenames.push_back({ fileChecksumOffset, 0, PDB::CodeView::DBI::ChecksumKind::None, 0, {0} });
+
+						sections.push_back({ sectionIndex, sectionOffset, lines.size() });
+
+						// initially set code size of first line to 0, will be updated in loop below.
+						lines.push_back({ firstLine.linenumStart, 0, filenameIndex });
+
+						for(uint32_t i = 1, size = linesBlockHeader->numLines; i < size; ++i)
+						{
+							const PDB::CodeView::DBI::Line& line = blocklines[i];
+
+							// calculate code size of previous line by using the current line offset.
+							lines.back().codeSize = line.offset - blocklines[i-1].offset;
+
+							sections.push_back({ sectionIndex, sectionOffset + line.offset, lines.size() });
+							lines.push_back({ line.linenumStart, 0, filenameIndex });
+						}
+
+						// calc code size of last line
+						lines.back().codeSize = lineSection->linesHeader.codeSize - blocklines[linesBlockHeader->numLines-1].offset;
+
+						// columns are optional
+						if (blockColumns == nullptr)
+						{
+							return;
+						}
+
+						for (uint32_t i = 0, size = linesBlockHeader->numLines; i < size; ++i)
+						{
+							const PDB::CodeView::DBI::Column& column = blockColumns[i];
+							(void)column;
+						}
+					});
+				}
+				else if (lineSection->header.kind == PDB::CodeView::DBI::DebugSubsectionKind::S_FILECHECKSUMS)
+				{
+					// how to read checksums and their filenames from the Names Stream
+					moduleLineStream.ForEachFileChecksum(lineSection, [&namesStream](const PDB::CodeView::DBI::FileChecksumHeader* fileChecksumHeader)
+					{
+						const char* filename = namesStream.GetFilename(fileChecksumHeader->filenameOffset);
+						(void)filename;
+					});
+
+					// store the checksum header for the module, as there might be more lines after the checksums.
+					// so lines will get their checksum header values assigned after processing all line sections in the module.
+					PDB_ASSERT(moduleFileChecksumHeader == nullptr, "Module File Checksum Header already set");
+					moduleFileChecksumHeader = &lineSection->checksumHeader;
+				}
+				else if (lineSection->header.kind == PDB::CodeView::DBI::DebugSubsectionKind::S_INLINEELINES)
+				{
+					if (lineSection->inlineeHeader.kind == PDB::CodeView::DBI::InlineeSourceLineKind::Signature)
+					{
+						moduleLineStream.ForEachInlineeSourceLine(lineSection, [](const PDB::CodeView::DBI::InlineeSourceLine* inlineeSourceLine)
+						{
+							(void)inlineeSourceLine;
+
+						});
+					}
+					else
+					{
+						moduleLineStream.ForEachInlineeSourceLineEx(lineSection, [](const PDB::CodeView::DBI::InlineeSourceLineEx* inlineeSourceLineEx)
+						{
+							for (uint32_t i = 0; i < inlineeSourceLineEx->extraLines; ++i)
+							{
+								const uint32_t checksumOffset = inlineeSourceLineEx->extrafileChecksumOffsets[i];
+								(void)checksumOffset;
+							}
+						});
+					}
+				}
+				else
+				{
+					PDB_ASSERT(false, "Line Section kind 0x%X not handled", static_cast<uint32_t>(lineSection->header.kind));
+				}
+			});
+	
+			// assign checksum values for each filename added in this module
+			for (size_t i = moduleFilenamesStartIndex, size = filenames.size(); i < size; ++i)
+			{
+				Filename& filename = filenames[i];
+
+				// look up the filename's checksum header in the module's checksums section
+				const PDB::CodeView::DBI::FileChecksumHeader* checksumHeader = PDB::Pointer::Offset<const PDB::CodeView::DBI::FileChecksumHeader*>(moduleFileChecksumHeader, filename.fileChecksumOffset);
+
+				PDB_ASSERT(checksumHeader->checksumKind >= PDB::CodeView::DBI::ChecksumKind::None && 
+							checksumHeader->checksumKind <= PDB::CodeView::DBI::ChecksumKind::SHA256,
+							"Invalid checksum kind %u", static_cast<uint16_t>(checksumHeader->checksumKind));
+
+				// store checksum values in filname struct
+				filename.namesFilenameOffset = checksumHeader->filenameOffset;
+				filename.checksumKind = checksumHeader->checksumKind;
+				filename.checksumSize = checksumHeader->checksumSize;
+				std::memcpy(filename.checksum, checksumHeader->checksum, checksumHeader->checksumSize);
+			}
+		}
+
+		scope.Done(modules.GetLength());
+
+		TimedScope sortScope("std::sort sections");
+
+		// sort sections, so we can iterate over lines by address order.
+		std::sort(sections.begin(), sections.end(), [](const Section& lhs, const Section& rhs)
+		{
+			if (lhs.index == rhs.index)
+			{
+				return lhs.offset < rhs.offset;
+			}
+
+			return lhs.index < rhs.index;
+		});
+
+		sortScope.Done(sections.size());
+
+// Disabled by default, as it will print a lot of lines for large PDBs :-)
+#if 0
+		// DIA2Dump style lines output
+		static const char hexChars[17] = "0123456789ABCDEF";
+		char checksumString[128];
+
+		printf("*** LINES RAW PDB\n");
+
+		const char* prevFilename = nullptr;
+
+		for (const Section& section : sections)
+		{
+			const Line& line = lines[section.lineIndex];
+			const Filename& lineFilename = filenames[line.filenameIndex];
+
+			const char* filename = namesStream.GetFilename(lineFilename.namesFilenameOffset);
+			
+			const uint32_t rva = imageSectionStream.ConvertSectionOffsetToRVA(section.index, section.offset);
+
+			// only print filename for a line if it is different from the previous one.
+			if (filename != prevFilename)
+			{
+				for (size_t i = 0, j = 0; i < lineFilename.checksumSize; i++, j+=2)
+				{
+					checksumString[j]   = hexChars[lineFilename.checksum[i] >> 4];
+					checksumString[j+1] = hexChars[lineFilename.checksum[i] & 0xF];
+				}
+
+				checksumString[lineFilename.checksumSize * 2] = '\0';
+
+				printf("	line %u at [0x%08X][0x%04X:0x%08X], len = 0x%X %s (0x%02X: %s)\n",
+					line.lineNumber, rva, section.index, section.offset, line.codeSize,
+					filename, static_cast<uint32_t>(lineFilename.checksumKind), checksumString);
+	
+				prevFilename = filename;
+			}
+			else
+			{
+				printf("	line %u at [0x%08X][0x%04X:0x%08X], len = 0x%X\n",
+					line.lineNumber, rva, section.index, section.offset, line.codeSize);
+			}
+		}
+#endif
+	}
+}