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, 0 insertions, 89 deletions

diff --git a/src/zen/cmds/trace_cmd.cpp b/src/zen/cmds/trace_cmd.cpp
deleted file mode 100644
index 54c0f080d..000000000
--- a/src/zen/cmds/trace_cmd.cpp
+++ /dev/null
@@ -1,89 +0,0 @@
-// Copyright Epic Games, Inc. All Rights Reserved.
-
-#include "trace_cmd.h"
-#include <zencore/logging.h>
-#include <zenhttp/httpclient.h>
-#include <zenhttp/httpcommon.h>
-
-using namespace std::literals;
-
-namespace zen {
-
-TraceCommand::TraceCommand()
-{
-	m_Options.add_options()("h,help", "Print help");
-	m_Options.add_option("", "u", "hosturl", kHostUrlHelp, cxxopts::value(m_HostName)->default_value(""), "<hosturl>");
-	m_Options.add_option("", "s", "stop", "Stop tracing", cxxopts::value(m_Stop)->default_value("false"), "<stop>");
-	m_Options.add_option("", "", "host", "Start tracing to host", cxxopts::value(m_TraceHost), "<hostip>");
-	m_Options.add_option("", "", "file", "Start tracing to file", cxxopts::value(m_TraceFile), "<filepath>");
-}
-
-TraceCommand::~TraceCommand() = default;
-
-void
-TraceCommand::Run(const ZenCliOptions& GlobalOptions, int argc, char** argv)
-{
-	ZEN_UNUSED(GlobalOptions);
-
-	if (!ParseOptions(argc, argv))
-	{
-		return;
-	}
-
-	m_HostName = ResolveTargetHostSpec(m_HostName);
-
-	if (m_HostName.empty())
-	{
-		throw OptionParseException("Unable to resolve server specification", m_Options.help());
-	}
-
-	zen::HttpClient Http = CreateHttpClient(m_HostName);
-
-	if (m_Stop)
-	{
-		if (zen::HttpClient::Response Response = Http.Post("/admin/trace/stop"sv))
-		{
-			ZEN_CONSOLE("OK: {}", Response.ToText());
-		}
-		else
-		{
-			Response.ThrowError("Trace stop failed");
-		}
-		return;
-	}
-
-	std::string StartArg;
-	if (!m_TraceHost.empty())
-	{
-		StartArg = fmt::format("host={}", m_TraceHost);
-	}
-	else if (!m_TraceFile.empty())
-	{
-		StartArg = fmt::format("file={}", m_TraceFile);
-	}
-
-	if (!StartArg.empty())
-	{
-		if (zen::HttpClient::Response Response = Http.Post(fmt::format("/admin/trace/start?{}"sv, StartArg)))
-		{
-			ZEN_CONSOLE("OK: {}", Response.ToText());
-		}
-		else
-		{
-			Response.ThrowError("Trace start failed");
-		}
-	}
-	else
-	{
-		if (zen::HttpClient::Response Response = Http.Get("/admin/trace"sv))
-		{
-			ZEN_CONSOLE("OK: {}", Response.ToText());
-		}
-		else
-		{
-			Response.ThrowError("Trace status failed");
-		}
-	}
-}
-
-}  // namespace zen