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, 169 insertions, 0 deletions

diff --git a/thirdparty/raw_pdb/src/PDB_CoalescedMSFStream.cpp b/thirdparty/raw_pdb/src/PDB_CoalescedMSFStream.cpp
new file mode 100644
index 000000000..fe544e4e9
--- /dev/null
+++ b/thirdparty/raw_pdb/src/PDB_CoalescedMSFStream.cpp
@@ -0,0 +1,169 @@
+// 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_CoalescedMSFStream.h"
+#include "PDB_Util.h"
+#include "PDB_DirectMSFStream.h"
+#include "Foundation/PDB_PointerUtil.h"
+#include "Foundation/PDB_Memory.h"
+#include "Foundation/PDB_CRT.h"
+
+
+namespace
+{
+	// ------------------------------------------------------------------------------------------------
+	// ------------------------------------------------------------------------------------------------
+	PDB_NO_DISCARD static bool AreBlockIndicesContiguous(const uint32_t* blockIndices, uint32_t blockSize, uint32_t streamSize) PDB_NO_EXCEPT
+	{
+		const uint32_t blockCount = PDB::ConvertSizeToBlockCount(streamSize, blockSize);
+
+		// start with the first index, checking if all following indices are contiguous (N, N+1, N+2, ...)
+		uint32_t expectedIndex = blockIndices[0];
+		for (uint32_t i = 1u; i < blockCount; ++i)
+		{
+			++expectedIndex;
+			if (blockIndices[i] != expectedIndex)
+			{
+				return false;
+			}
+		}
+
+		return true;
+	}
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB::CoalescedMSFStream::CoalescedMSFStream(void) PDB_NO_EXCEPT
+	: m_ownedData(nullptr)
+	, m_data(nullptr)
+	, m_size(0u)
+{
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB::CoalescedMSFStream::CoalescedMSFStream(CoalescedMSFStream&& other) PDB_NO_EXCEPT
+	: m_ownedData(PDB_MOVE(other.m_ownedData))
+	, m_data(PDB_MOVE(other.m_data))
+	, m_size(PDB_MOVE(other.m_size))
+{
+	other.m_ownedData = nullptr;
+	other.m_data = nullptr;
+	other.m_size = 0u;
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB::CoalescedMSFStream& PDB::CoalescedMSFStream::operator=(CoalescedMSFStream&& other) PDB_NO_EXCEPT
+{
+	if (this != &other)
+	{
+		PDB_DELETE_ARRAY(m_ownedData);
+
+		m_ownedData = PDB_MOVE(other.m_ownedData);
+		m_data = PDB_MOVE(other.m_data);
+		m_size = PDB_MOVE(other.m_size);
+
+		other.m_ownedData = nullptr;
+		other.m_data = nullptr;
+		other.m_size = 0u;
+	}
+
+	return *this;
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB::CoalescedMSFStream::CoalescedMSFStream(const void* data, uint32_t blockSize, const uint32_t* blockIndices, uint32_t streamSize) PDB_NO_EXCEPT
+	: m_ownedData(nullptr)
+	, m_data(nullptr)
+	, m_size(streamSize)
+{
+	if (AreBlockIndicesContiguous(blockIndices, blockSize, streamSize))
+	{
+		// fast path, all block indices are contiguous, so we don't have to copy any data at all.
+		// instead, we directly point into the memory-mapped file at the correct offset.
+		const uint32_t index = blockIndices[0];
+		const size_t fileOffset = PDB::ConvertBlockIndexToFileOffset(index, blockSize);
+		m_data = Pointer::Offset<const Byte*>(data, fileOffset);
+	}
+	else
+	{
+		// slower path, we need to copy disjunct blocks into our own data array, block by block
+		m_ownedData = PDB_NEW_ARRAY(Byte, streamSize);
+		m_data = m_ownedData;
+
+		Byte* destination = m_ownedData;
+
+		// copy full blocks first
+		const uint32_t fullBlockCount = streamSize / blockSize;
+		for (uint32_t i = 0u; i < fullBlockCount; ++i)
+		{
+			const uint32_t index = blockIndices[i];
+
+			// read one single block at the correct offset in the stream
+			const size_t fileOffset = PDB::ConvertBlockIndexToFileOffset(index, blockSize);
+			const void* sourceData = Pointer::Offset<const void*>(data, fileOffset);
+			memcpy(destination, sourceData, blockSize);
+
+			destination += blockSize;
+		}
+
+		// account for non-full blocks
+		const uint32_t remainingBytes = streamSize - (fullBlockCount * blockSize);
+		if (remainingBytes != 0u)
+		{
+			const uint32_t index = blockIndices[fullBlockCount];
+
+			// read remaining bytes at correct offset in the stream
+			const size_t fileOffset = PDB::ConvertBlockIndexToFileOffset(index, blockSize);
+			const void* sourceData = Pointer::Offset<const void*>(data, fileOffset);
+			memcpy(destination, sourceData, remainingBytes);
+		}
+	}
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB::CoalescedMSFStream::CoalescedMSFStream(const DirectMSFStream& directStream, uint32_t size, uint32_t offset) PDB_NO_EXCEPT
+	: m_ownedData(nullptr)
+	, m_data(nullptr)
+	, m_size(size)
+{
+	const DirectMSFStream::IndexAndOffset indexAndOffset = directStream.GetBlockIndexForOffset(offset);
+
+	// Note: we need to add the offset within the block to the size of the stream to determine if the block
+	// indices are contiguous. This is needed to deal with the case where reading the requested number of bytes
+	// from the specified offset would cross a block boundary. For example, if the offset within the block is
+	// 64 and we want to read 4096 bytes with a block size of 4096, we need to consider *two* block indices,
+	// not *one*, even though 4096 / 4096 = 1.
+	if (AreBlockIndicesContiguous(directStream.GetBlockIndices() + indexAndOffset.index, directStream.GetBlockSize(), indexAndOffset.offsetWithinBlock + size))
+	{
+		// fast path, all block indices inside the direct stream from (data + offset) to (data + offset + size) are contiguous
+		const size_t offsetWithinData = directStream.GetDataOffsetForIndexAndOffset(indexAndOffset);
+		m_data = Pointer::Offset<const Byte*>(directStream.GetData(), offsetWithinData);
+	}
+	else
+	{
+		// slower path, we need to copy from disjunct blocks, which is performed by the direct stream
+		m_ownedData = PDB_NEW_ARRAY(Byte, size);
+		m_data = m_ownedData;
+
+		directStream.ReadAtOffset(m_ownedData, size, offset);
+	}
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB::CoalescedMSFStream::~CoalescedMSFStream(void) PDB_NO_EXCEPT
+{
+	PDB_DELETE_ARRAY(m_ownedData);
+}