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, 47 insertions, 0 deletions

diff --git a/thirdparty/raw_pdb/src/PDB_ImageSectionStream.cpp b/thirdparty/raw_pdb/src/PDB_ImageSectionStream.cpp
new file mode 100644
index 000000000..3d495ad0b
--- /dev/null
+++ b/thirdparty/raw_pdb/src/PDB_ImageSectionStream.cpp
@@ -0,0 +1,47 @@
+// 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_ImageSectionStream.h"
+#include "PDB_RawFile.h"
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB::ImageSectionStream::ImageSectionStream(void) PDB_NO_EXCEPT
+	: m_stream()
+	, m_headers(nullptr)
+	, m_count(0u)
+{
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB::ImageSectionStream::ImageSectionStream(const RawFile& file, uint16_t streamIndex) PDB_NO_EXCEPT
+	: m_stream(file.CreateMSFStream<CoalescedMSFStream>(streamIndex))
+	, m_headers(m_stream.GetDataAtOffset<IMAGE_SECTION_HEADER>(0u))
+	, m_count(m_stream.GetSize() / sizeof(IMAGE_SECTION_HEADER))
+{
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB_NO_DISCARD uint32_t PDB::ImageSectionStream::ConvertSectionOffsetToRVA(uint16_t oneBasedSectionIndex, uint32_t offsetInSection) const PDB_NO_EXCEPT
+{
+	if (oneBasedSectionIndex == 0u)
+	{
+		// should never happen, but prevent underflow
+		return 0u;
+	}
+	else if (oneBasedSectionIndex > m_count)
+	{
+		// this symbol is "contained" in a section that is neither part of the PDB, nor the EXE.
+		// it is a special compiler-generated or linker-generated symbol such as CFG symbols (e.g. __guard_fids_count, __guard_flags).
+		// we can safely ignore those symbols.
+		return 0u;
+	}
+
+	return m_headers[oneBasedSectionIndex - 1u].VirtualAddress + offsetInSection;
+}