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, 107 insertions, 0 deletions

diff --git a/src/zen-test/trace-tests.cpp b/src/zen-test/trace-tests.cpp
new file mode 100644
index 000000000..e57d30e6c
--- /dev/null
+++ b/src/zen-test/trace-tests.cpp
@@ -0,0 +1,107 @@
+// Copyright Epic Games, Inc. All Rights Reserved.
+
+#include <zencore/zencore.h>
+
+#if ZEN_WITH_TESTS
+
+#	include "zen-test.h"
+
+#	include <zencore/filesystem.h>
+#	include <zencore/testing.h>
+
+#	include <system_error>
+
+namespace zen::tests {
+
+using namespace std::literals;
+
+TEST_SUITE_BEGIN("zen.trace");
+
+TEST_CASE("help.top_level")
+{
+	ZenCommandResult Result = RunZen("trace --help");
+	CHECK_EQ(Result.ExitCode, 0);
+	CHECK_MESSAGE(Result.Output.find("subcommands:") != std::string::npos, Result.Output);
+	CHECK_MESSAGE(Result.Output.find("analyze") != std::string::npos, Result.Output);
+	CHECK_MESSAGE(Result.Output.find("inspect") != std::string::npos, Result.Output);
+	CHECK_MESSAGE(Result.Output.find("serve") != std::string::npos, Result.Output);
+}
+
+TEST_CASE("help.inspect")
+{
+	ZenCommandResult Result = RunZen("trace inspect --help");
+	CHECK_EQ(Result.ExitCode, 0);
+	CHECK_MESSAGE(Result.Output.find("Inspect event schemas") != std::string::npos, Result.Output);
+}
+
+TEST_CASE("inspect.missing_file")
+{
+	ZenCommandResult Result = RunZen("trace inspect this-file-does-not-exist.utrace");
+	CHECK_NE(Result.ExitCode, 0);
+	CHECK_MESSAGE(Result.Output.find("File not found") != std::string::npos, Result.Output);
+}
+
+TEST_CASE("inspect.generated_tracefile")
+{
+	const std::filesystem::path DataDir	  = TestEnv.CreateNewTestDir();
+	const std::filesystem::path TraceFile = DataDir / "powercycle-trace.utrace";
+
+	ZenServerInstance Instance(TestEnv);
+	Instance.SetDataDir(DataDir);
+
+	ExtendableStringBuilder<512> ServerArgs;
+	ServerArgs << "--tracefile=\"";
+	PathToUtf8(TraceFile.c_str(), ServerArgs);
+	ServerArgs << "\" --powercycle";
+
+	Instance.SpawnServer(TestEnv.GetNewPortNumber(), ServerArgs.ToView());
+	CHECK_MESSAGE(Instance.WaitUntilReady(10000), Instance.GetLogOutput());
+
+	if (Instance.IsRunning())
+	{
+		std::error_code Ec;
+		CHECK_MESSAGE(Instance.WaitUntilExited(10000, Ec), Instance.GetLogOutput());
+		CHECK_MESSAGE(!Ec, Ec.message());
+	}
+
+	CHECK_EQ(Instance.Shutdown(), 0);
+	CHECK_MESSAGE(std::filesystem::exists(TraceFile), TraceFile.string());
+	CHECK_MESSAGE(std::filesystem::file_size(TraceFile) > 0, TraceFile.string());
+
+	ExtendableStringBuilder<512> InspectArgs;
+	InspectArgs << "trace inspect \"";
+	PathToUtf8(TraceFile.c_str(), InspectArgs);
+	InspectArgs << "\"";
+
+	ZenCommandResult InspectResult = RunZen(InspectArgs.ToView());
+	CHECK_EQ(InspectResult.ExitCode, 0);
+	CHECK_MESSAGE(InspectResult.Output.find("Trace:") != std::string::npos, InspectResult.Output);
+	CHECK_MESSAGE(InspectResult.Output.find("Events:") != std::string::npos, InspectResult.Output);
+	CHECK_MESSAGE(InspectResult.Output.find("Types:") != std::string::npos, InspectResult.Output);
+	CHECK_MESSAGE(InspectResult.Output.find("Event Schemas:") != std::string::npos, InspectResult.Output);
+	CHECK_MESSAGE(InspectResult.Output.find("Events:  0") == std::string::npos, InspectResult.Output);
+	CHECK_MESSAGE(InspectResult.Output.find("Types:   0") == std::string::npos, InspectResult.Output);
+	CHECK_MESSAGE(InspectResult.Output.find("(uid=") != std::string::npos, InspectResult.Output);
+	CHECK_MESSAGE(InspectResult.Output.find("events=") != std::string::npos, InspectResult.Output);
+
+	ExtendableStringBuilder<512> AnalyzeArgs;
+	AnalyzeArgs << "trace analyze --no-cache --symbols=off \"";
+	PathToUtf8(TraceFile.c_str(), AnalyzeArgs);
+	AnalyzeArgs << "\"";
+
+	ZenCommandResult AnalyzeResult = RunZen(AnalyzeArgs.ToView());
+	CHECK_EQ(AnalyzeResult.ExitCode, 0);
+	CHECK_MESSAGE(AnalyzeResult.Output.find("Trace:") != std::string::npos, AnalyzeResult.Output);
+	CHECK_MESSAGE(AnalyzeResult.Output.find("Size:") != std::string::npos, AnalyzeResult.Output);
+	CHECK_MESSAGE(AnalyzeResult.Output.find("Events:") != std::string::npos, AnalyzeResult.Output);
+	CHECK_MESSAGE(AnalyzeResult.Output.find("Duration:") != std::string::npos, AnalyzeResult.Output);
+	CHECK_MESSAGE(AnalyzeResult.Output.find("Threads:") != std::string::npos, AnalyzeResult.Output);
+	CHECK_MESSAGE(AnalyzeResult.Output.find("Modules:") != std::string::npos, AnalyzeResult.Output);
+	CHECK_MESSAGE(AnalyzeResult.Output.find("Parsed:") != std::string::npos, AnalyzeResult.Output);
+}
+
+TEST_SUITE_END();
+
+}  // namespace zen::tests
+
+#endif