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, 96 insertions, 0 deletions

diff --git a/thirdparty/raw_pdb/src/Examples/ExampleContributions.cpp b/thirdparty/raw_pdb/src/Examples/ExampleContributions.cpp
new file mode 100644
index 000000000..93c509117
--- /dev/null
+++ b/thirdparty/raw_pdb/src/Examples/ExampleContributions.cpp
@@ -0,0 +1,96 @@
+// 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 "PDB_RawFile.h"
+#include "PDB_DBIStream.h"
+
+
+namespace
+{
+	// we don't have to store std::string in the contributions, since all the data is memory-mapped anyway.
+	// we do it in this example to ensure that we don't "cheat" when reading the PDB file. memory-mapped data will only
+	// be faulted into the process once it's touched, so actually copying the string data makes us touch the needed data,
+	// giving us a real performance measurement.
+	struct Contribution
+	{
+		std::string objectFile;
+		uint32_t rva;
+		uint32_t size;
+	};
+}
+
+
+void ExampleContributions(const PDB::RawFile& rawPdbFile, const PDB::DBIStream& dbiStream);
+void ExampleContributions(const PDB::RawFile& rawPdbFile, const PDB::DBIStream& dbiStream)
+{
+	TimedScope total("\nRunning example \"Contributions\"");
+
+	// in order to keep the example easy to understand, we load the PDB data serially.
+	// note that this can be improved a lot by reading streams concurrently.
+
+	// 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 matching contributions against files
+	TimedScope moduleScope("Reading module info stream");
+	const PDB::ModuleInfoStream moduleInfoStream = dbiStream.CreateModuleInfoStream(rawPdbFile);
+	moduleScope.Done();
+
+
+	// read contribution stream
+	TimedScope contributionScope("Reading section contribution stream");
+	const PDB::SectionContributionStream sectionContributionStream = dbiStream.CreateSectionContributionStream(rawPdbFile);
+	contributionScope.Done();
+
+	std::vector<Contribution> contributions;
+	{
+		TimedScope scope("Storing contributions");
+
+		const PDB::ArrayView<PDB::DBI::SectionContribution> sectionContributions = sectionContributionStream.GetContributions();
+		const size_t count = sectionContributions.GetLength();
+
+		contributions.reserve(count);
+
+		for (const PDB::DBI::SectionContribution& contribution : sectionContributions)
+		{
+			const uint32_t rva = imageSectionStream.ConvertSectionOffsetToRVA(contribution.section, contribution.offset);
+			if (rva == 0u)
+			{
+				printf("Contribution has invalid RVA\n");
+				continue;
+			}
+
+			const PDB::ModuleInfoStream::Module& module = moduleInfoStream.GetModule(contribution.moduleIndex);
+
+			contributions.push_back(Contribution { module.GetName().Decay(), rva, contribution.size });
+		}
+		
+		scope.Done(count);
+	}
+
+	TimedScope sortScope("std::sort contributions");
+	std::sort(contributions.begin(), contributions.end(), [](const Contribution& lhs, const Contribution& rhs)
+	{
+		return lhs.size > rhs.size;
+	});
+	sortScope.Done();
+
+	total.Done();
+
+	// log the 20 largest contributions
+	{
+		printf("20 largest contributions:\n");
+
+		const size_t countToShow = std::min<size_t>(20ul, contributions.size());
+		for (size_t i = 0u; i < countToShow; ++i)
+		{
+			const Contribution& contribution = contributions[i];
+			printf("%zu: %u bytes from %s\n", i + 1u, contribution.size, contribution.objectFile.c_str());
+		}
+	}
+}