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, 115 insertions, 0 deletions

diff --git a/thirdparty/raw_pdb/src/PDB_DirectMSFStream.cpp b/thirdparty/raw_pdb/src/PDB_DirectMSFStream.cpp
new file mode 100644
index 000000000..442dc7637
--- /dev/null
+++ b/thirdparty/raw_pdb/src/PDB_DirectMSFStream.cpp
@@ -0,0 +1,115 @@
+// 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_DirectMSFStream.h"
+#include "Foundation/PDB_PointerUtil.h"
+#include "Foundation/PDB_BitUtil.h"
+#include "Foundation/PDB_Assert.h"
+#include "Foundation/PDB_CRT.h"
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB::DirectMSFStream::DirectMSFStream(void) PDB_NO_EXCEPT
+	: m_data(nullptr)
+	, m_blockIndices(nullptr)
+	, m_blockSize(0u)
+	, m_size(0u)
+	, m_blockSizeLog2(0u)
+{
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB::DirectMSFStream::DirectMSFStream(const void* data, uint32_t blockSize, const uint32_t* blockIndices, uint32_t streamSize) PDB_NO_EXCEPT
+	: m_data(data)
+	, m_blockIndices(blockIndices)
+	, m_blockSize(blockSize)
+	, m_size(streamSize)
+	, m_blockSizeLog2(BitUtil::FindFirstSetBit(blockSize))
+{
+	PDB_ASSERT(BitUtil::IsPowerOfTwo(blockSize), "MSF block size must be a power of two.");
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+void PDB::DirectMSFStream::ReadAtOffset(void* destination, size_t size, size_t offset) const PDB_NO_EXCEPT
+{
+	PDB_ASSERT(destination != nullptr, "Destination buffer not set");
+	PDB_ASSERT(offset + size <= m_size, "Not enough data left to read.");
+
+	// work out which block and offset within the block the read offset corresponds to
+	size_t blockIndex = offset >> m_blockSizeLog2;
+	const size_t offsetWithinBlock = offset & (m_blockSize - 1u);
+
+	// work out the offset within the data based on the block indices
+	size_t offsetWithinData = (static_cast<size_t>(m_blockIndices[blockIndex]) << m_blockSizeLog2) + offsetWithinBlock;
+	const size_t bytesLeftInBlock = m_blockSize - offsetWithinBlock;
+
+	if (bytesLeftInBlock >= size)
+	{
+		// fast path, all the data can be read in one go
+		const void* const sourceData = Pointer::Offset<const void*>(m_data, offsetWithinData);
+		memcpy(destination, sourceData, size);
+	}
+	else
+	{
+		// slower path, data is scattered across several blocks.
+		// read remaining bytes in current block first.
+		{
+			const void* const sourceData = Pointer::Offset<const void*>(m_data, offsetWithinData);
+			memcpy(destination, sourceData, bytesLeftInBlock);
+		}
+
+		// read remaining bytes from blocks
+		size_t bytesLeftToRead = size - bytesLeftInBlock;
+		while (bytesLeftToRead != 0u)
+		{
+			// advance to the next block
+			++blockIndex;
+			offsetWithinData = static_cast<size_t>(m_blockIndices[blockIndex]) << m_blockSizeLog2;
+
+			void* const destinationData = Pointer::Offset<void*>(destination, size - bytesLeftToRead);
+			const void* const sourceData = Pointer::Offset<const void*>(m_data, offsetWithinData);
+
+			if (bytesLeftToRead > m_blockSize)
+			{
+				// copy a whole block at once
+				memcpy(destinationData, sourceData, m_blockSize);
+				bytesLeftToRead -= m_blockSize;
+			}
+			else
+			{
+				// copy remaining bytes
+				memcpy(destinationData, sourceData, bytesLeftToRead);
+				bytesLeftToRead -= bytesLeftToRead;
+			}
+		}
+	}
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB_NO_DISCARD PDB::DirectMSFStream::IndexAndOffset PDB::DirectMSFStream::GetBlockIndexForOffset(uint32_t offset) const PDB_NO_EXCEPT
+{
+	// work out which block and offset within the block the offset corresponds to
+	const uint32_t blockIndex = offset >> m_blockSizeLog2;
+	const uint32_t offsetWithinBlock = offset & (m_blockSize - 1u);
+
+	return IndexAndOffset { blockIndex, offsetWithinBlock };
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB_NO_DISCARD size_t PDB::DirectMSFStream::GetDataOffsetForIndexAndOffset(const IndexAndOffset& indexAndOffset) const PDB_NO_EXCEPT
+{
+	// work out the offset within the data based on the block indices
+	const size_t offsetWithinData = (static_cast<size_t>(m_blockIndices[indexAndOffset.index]) << m_blockSizeLog2) + indexAndOffset.offsetWithinBlock;
+
+	return offsetWithinData;
+}