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, 147 insertions, 0 deletions

diff --git a/thirdparty/raw_pdb/src/PDB_RawFile.cpp b/thirdparty/raw_pdb/src/PDB_RawFile.cpp
new file mode 100644
index 000000000..f135efe66
--- /dev/null
+++ b/thirdparty/raw_pdb/src/PDB_RawFile.cpp
@@ -0,0 +1,147 @@
+// 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_RawFile.h"
+#include "PDB_Types.h"
+#include "PDB_Util.h"
+#include "PDB_DirectMSFStream.h"
+#include "Foundation/PDB_PointerUtil.h"
+#include "Foundation/PDB_Memory.h"
+#include "Foundation/PDB_Assert.h"
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB::RawFile::RawFile(RawFile&& other) PDB_NO_EXCEPT
+	: m_data(PDB_MOVE(other.m_data))
+	, m_superBlock(PDB_MOVE(other.m_superBlock))
+	, m_directoryStream(PDB_MOVE(other.m_directoryStream))
+	, m_streamCount(PDB_MOVE(other.m_streamCount))
+	, m_streamSizes(PDB_MOVE(other.m_streamSizes))
+	, m_streamBlocks(PDB_MOVE(other.m_streamBlocks))
+{
+	other.m_data = nullptr;
+	other.m_superBlock = nullptr;
+	other.m_streamCount = 0u;
+	other.m_streamSizes = nullptr;
+	other.m_streamBlocks = nullptr;
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB::RawFile& PDB::RawFile::operator=(RawFile&& other) PDB_NO_EXCEPT
+{
+	if (this != &other)
+	{
+		PDB_DELETE_ARRAY(m_streamBlocks);
+
+		m_data = PDB_MOVE(other.m_data);
+		m_superBlock = PDB_MOVE(other.m_superBlock);
+		m_directoryStream = PDB_MOVE(other.m_directoryStream);
+		m_streamCount = PDB_MOVE(other.m_streamCount);
+		m_streamSizes = PDB_MOVE(other.m_streamSizes);
+		m_streamBlocks = PDB_MOVE(other.m_streamBlocks);
+
+		other.m_data = nullptr;
+		other.m_superBlock = nullptr;
+		other.m_streamCount = 0u;
+		other.m_streamSizes = nullptr;
+		other.m_streamBlocks = nullptr;
+	}
+
+	return *this;
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB::RawFile::RawFile(const void* data) PDB_NO_EXCEPT
+	: m_data(data)
+	, m_superBlock(Pointer::Offset<const SuperBlock*>(data, 0u))
+	, m_directoryStream()
+	, m_streamCount(0u)
+	, m_streamSizes(nullptr)
+	, m_streamBlocks(nullptr)
+{
+	// the SuperBlock stores an array of indices of blocks that make up the indices of directory blocks, which need to be stitched together to form the directory.
+	// the blocks holding the indices of directory blocks are not necessarily contiguous, so they need to be coalesced first.
+	const uint32_t directoryBlockCount = PDB::ConvertSizeToBlockCount(m_superBlock->directorySize, m_superBlock->blockSize);
+
+	// the directory is made up of directoryBlockCount blocks, so we need that many indices to be read from the blocks that make up the indices
+	CoalescedMSFStream directoryIndicesStream(data, m_superBlock->blockSize, m_superBlock->directoryBlockIndices, directoryBlockCount * sizeof(uint32_t));
+
+	// these are the indices of blocks making up the directory stream, now guaranteed to be contiguous
+	const uint32_t* directoryIndices = directoryIndicesStream.GetDataAtOffset<uint32_t>(0u);
+
+	m_directoryStream = CoalescedMSFStream(data, m_superBlock->blockSize, directoryIndices, m_superBlock->directorySize);
+
+	// https://llvm.org/docs/PDB/MsfFile.html#the-stream-directory
+	// parse the directory from its contiguous version. the directory matches the following struct:
+	//	struct StreamDirectory
+	//	{
+	//		uint32_t streamCount;
+	//		uint32_t streamSizes[streamCount];
+	//		uint32_t streamBlocks[streamCount][];
+	//	};
+	m_streamCount = *m_directoryStream.GetDataAtOffset<uint32_t>(0u);
+
+	// we can assign pointers into the stream directly, since the RawFile keeps ownership of the directory stream
+	m_streamSizes = m_directoryStream.GetDataAtOffset<uint32_t>(sizeof(uint32_t));
+	const uint32_t* directoryStreamBlocks = m_directoryStream.GetDataAtOffset<uint32_t>(sizeof(uint32_t) + sizeof(uint32_t) * m_streamCount);
+
+	// prepare indices for directly accessing individual streams
+	m_streamBlocks = PDB_NEW_ARRAY(const uint32_t*, m_streamCount);
+
+	const uint32_t* indicesForCurrentBlock = directoryStreamBlocks;
+	for (uint32_t i = 0u; i < m_streamCount; ++i)
+	{
+		const uint32_t sizeInBytes = GetStreamSize(i);
+		const uint32_t blockCount = ConvertSizeToBlockCount(sizeInBytes, m_superBlock->blockSize);
+		m_streamBlocks[i] = indicesForCurrentBlock;
+		
+		indicesForCurrentBlock += blockCount;
+	}
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB::RawFile::~RawFile(void) PDB_NO_EXCEPT
+{
+	PDB_DELETE_ARRAY(m_streamBlocks);
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+template <typename T>
+PDB_NO_DISCARD T PDB::RawFile::CreateMSFStream(uint32_t streamIndex) const PDB_NO_EXCEPT
+{
+	PDB_ASSERT(streamIndex != PDB::NilStreamIndex, "Invalid stream index.");
+	PDB_ASSERT(streamIndex < m_streamCount, "Invalid stream index.");
+
+	return T(m_data, m_superBlock->blockSize, m_streamBlocks[streamIndex], GetStreamSize(streamIndex));
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+template <typename T>
+PDB_NO_DISCARD T PDB::RawFile::CreateMSFStream(uint32_t streamIndex, uint32_t streamSize) const PDB_NO_EXCEPT
+{
+	PDB_ASSERT(streamIndex != PDB::NilStreamIndex, "Invalid stream index.");
+	PDB_ASSERT(streamIndex < m_streamCount, "Invalid stream index.");
+	PDB_ASSERT(streamSize <= GetStreamSize(streamIndex), "Invalid stream size.");
+
+	return T(m_data, m_superBlock->blockSize, m_streamBlocks[streamIndex], streamSize);
+}
+
+
+// explicit template instantiation
+template PDB::CoalescedMSFStream PDB::RawFile::CreateMSFStream<PDB::CoalescedMSFStream>(uint32_t streamIndex) const PDB_NO_EXCEPT;
+template PDB::DirectMSFStream PDB::RawFile::CreateMSFStream<PDB::DirectMSFStream>(uint32_t streamIndex) const PDB_NO_EXCEPT;
+
+template PDB::CoalescedMSFStream PDB::RawFile::CreateMSFStream<PDB::CoalescedMSFStream>(uint32_t streamIndex, uint32_t streamSize) const PDB_NO_EXCEPT;
+template PDB::DirectMSFStream PDB::RawFile::CreateMSFStream<PDB::DirectMSFStream>(uint32_t streamIndex, uint32_t streamSize) const PDB_NO_EXCEPT;