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, 184 insertions, 0 deletions

diff --git a/thirdparty/raw_pdb/src/PDB_ModuleInfoStream.cpp b/thirdparty/raw_pdb/src/PDB_ModuleInfoStream.cpp
new file mode 100644
index 000000000..86040fffb
--- /dev/null
+++ b/thirdparty/raw_pdb/src/PDB_ModuleInfoStream.cpp
@@ -0,0 +1,184 @@
+// 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 "PDB_PCH.h"
+#include "PDB_ModuleInfoStream.h"
+#include "Foundation/PDB_Memory.h"
+#include "Foundation/PDB_CRT.h"
+
+namespace
+{
+	static constexpr const char* LinkerSymbolName("* Linker *");
+
+
+	// ------------------------------------------------------------------------------------------------
+	// ------------------------------------------------------------------------------------------------
+	PDB_NO_DISCARD static inline size_t EstimateModuleCount(size_t streamSize) PDB_NO_EXCEPT
+	{
+		// work out how many modules are stored in the stream at most.
+		// the module info is stored in variable-length records, so we can't determine the exact number without walking the stream.
+		return streamSize / sizeof(PDB::DBI::ModuleInfo);
+	}
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB::ModuleInfoStream::Module::Module(void) PDB_NO_EXCEPT
+	: m_info(nullptr)
+	, m_name(nullptr)
+	, m_nameLength(0u)
+	, m_objectName(nullptr)
+	, m_objectNameLength(0u)
+{
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB::ModuleInfoStream::Module::Module(const DBI::ModuleInfo* info, const char* name, size_t nameLength, const char* objectName, size_t objectNameLength) PDB_NO_EXCEPT
+	: m_info(info)
+	, m_name(name)
+	, m_nameLength(nameLength)
+	, m_objectName(objectName)
+	, m_objectNameLength(objectNameLength)
+{
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB_NO_DISCARD bool PDB::ModuleInfoStream::Module::HasSymbolStream(void) const PDB_NO_EXCEPT
+{
+	const uint16_t streamIndex = m_info->moduleSymbolStreamIndex;
+
+	// some modules don't have a symbol stream, i.e. no additional debug information is present.
+	// this usually happens when private symbols are stripped from a PDB.
+	return (streamIndex != 0xFFFFu);
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB_NO_DISCARD bool PDB::ModuleInfoStream::Module::HasLineStream(void) const PDB_NO_EXCEPT
+{
+	return (m_info->c13Size > 0);
+}
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB_NO_DISCARD PDB::ModuleSymbolStream PDB::ModuleInfoStream::Module::CreateSymbolStream(const RawFile& file) const PDB_NO_EXCEPT
+{
+	PDB_ASSERT(HasSymbolStream(), "Module symbol stream index is invalid.");
+
+	return ModuleSymbolStream(file, m_info->moduleSymbolStreamIndex, m_info->symbolSize);
+}
+
+PDB_NO_DISCARD PDB::ModuleLineStream PDB::ModuleInfoStream::Module::CreateLineStream(const RawFile& file) const PDB_NO_EXCEPT
+{
+	PDB_ASSERT(HasLineStream(), "Module line stream is not present.");
+
+	return ModuleLineStream(file, m_info->moduleSymbolStreamIndex, m_info->symbolSize + m_info->c11Size + m_info->c13Size, m_info->symbolSize + m_info->c11Size);
+}
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB::ModuleInfoStream::ModuleInfoStream(void) PDB_NO_EXCEPT
+	: m_stream()
+	, m_modules(nullptr)
+	, m_moduleCount(0u)
+{
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB::ModuleInfoStream::ModuleInfoStream(ModuleInfoStream&& other) PDB_NO_EXCEPT
+	: m_stream(PDB_MOVE(other.m_stream))
+	, m_modules(PDB_MOVE(other.m_modules))
+	, m_moduleCount(PDB_MOVE(other.m_moduleCount))
+{
+	other.m_modules = nullptr;
+	other.m_moduleCount = 0u;
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB::ModuleInfoStream& PDB::ModuleInfoStream::operator=(ModuleInfoStream&& other) PDB_NO_EXCEPT
+{
+	if (this != &other)
+	{
+		PDB_DELETE_ARRAY(m_modules);
+
+		m_stream = PDB_MOVE(other.m_stream);
+		m_modules = PDB_MOVE(other.m_modules);
+		m_moduleCount = PDB_MOVE(other.m_moduleCount);
+
+		other.m_modules = nullptr;
+		other.m_moduleCount = 0u;
+	}
+
+	return *this;
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB::ModuleInfoStream::ModuleInfoStream(const DirectMSFStream& directStream, uint32_t size, uint32_t offset) PDB_NO_EXCEPT
+	: m_stream(directStream, size, offset)
+	, m_modules(nullptr)
+	, m_moduleCount(0u)
+{
+	m_modules = PDB_NEW_ARRAY(Module, EstimateModuleCount(size));
+
+	size_t streamOffset = 0u;
+	while (streamOffset < size)
+	{
+		const DBI::ModuleInfo* moduleInfo = m_stream.GetDataAtOffset<const DBI::ModuleInfo>(streamOffset);
+		streamOffset += sizeof(DBI::ModuleInfo);
+
+		const char* name = m_stream.GetDataAtOffset<const char>(streamOffset);
+		const size_t nameLength = strlen(name);
+		streamOffset += nameLength + 1u;
+
+		const char* objectName = m_stream.GetDataAtOffset<const char>(streamOffset);
+		const size_t objectNameLength = strlen(objectName);
+		streamOffset += objectNameLength + 1u;
+
+		// the stream is aligned to 4 bytes
+		streamOffset = BitUtil::RoundUpToMultiple<size_t>(streamOffset, 4ul);
+
+		m_modules[m_moduleCount] = Module(moduleInfo, name, nameLength, objectName, objectNameLength);
+		++m_moduleCount;
+	}
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB::ModuleInfoStream::~ModuleInfoStream(void) PDB_NO_EXCEPT
+{
+	PDB_DELETE_ARRAY(m_modules);
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB_NO_DISCARD const PDB::ModuleInfoStream::Module* PDB::ModuleInfoStream::FindLinkerModule(void) const PDB_NO_EXCEPT
+{
+	const size_t count = m_moduleCount;
+	for (size_t i = 0u; i < count; ++i)
+	{
+		// with both MSVC cl.exe and Clang, the linker symbol is the last one to be stored, so start searching from the end
+		const Module& module = m_modules[count - i - 1u];
+
+		// check if this is the linker symbol
+		if (strcmp(module.GetName().Decay(), LinkerSymbolName) == 0)
+		{
+			return &module;
+		}
+	}
+
+	return nullptr;
+}