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, 45 insertions, 1 deletions

diff --git a/src/zen/xmake.lua b/src/zen/xmake.lua
index df249ade4..c4084231d 100644
--- a/src/zen/xmake.lua
+++ b/src/zen/xmake.lua
@@ -5,13 +5,57 @@ target("zen")
     add_headerfiles("**.h")
     add_files("**.cpp")
     add_files("zen.cpp", {unity_ignored  = true })
+    add_rules("utils.bin2c", {extensions = {".zip"}})
+    add_files(path.join(os.projectdir(), get_config("builddir") or get_config("buildir") or "build", "zen-frontend/zen-html.zip"))
     add_deps("zencore", "zenhttp", "zenremotestore", "zenstore", "zenutil")
     add_deps("zencompute", "zennet", "zentelemetry")
-    add_deps("cxxopts", "fmt")
+    add_deps("cxxopts", "fmt", "raw_pdb", "tourist")
     add_packages("json11")
     add_includedirs(".")
+    add_defines("ZEN_EMBED_ZEN_HTML_ZIP=1")
     set_symbols("debug")
 
+    on_load(function(target)
+        local html_dir = path.join(os.projectdir(), "src/zen/frontend/html")
+        local zip_dir = path.join(os.projectdir(), get_config("builddir") or get_config("buildir") or "build", "zen-frontend")
+        local zip_path = path.join(zip_dir, "zen-html.zip")
+
+        -- Check if zip needs regeneration
+        local need_update = not os.isfile(zip_path)
+        if not need_update then
+            local zip_mtime = os.mtime(zip_path)
+            for _, file in ipairs(os.files(path.join(html_dir, "**"))) do
+                if os.mtime(file) > zip_mtime then
+                    need_update = true
+                    break
+                end
+            end
+        end
+
+        if need_update then
+            print("Regenerating zen trace viewer frontend zip...")
+
+            os.tryrm(zip_path)
+            os.mkdir(zip_dir)
+
+            import("detect.tools.find_7z")
+            local cmd_7z = find_7z()
+            if cmd_7z then
+                os.execv(cmd_7z, {"a", "-bso0", zip_path, path.join(html_dir, "*")})
+            else
+                import("detect.tools.find_zip")
+                local zip_cmd = find_zip()
+                if zip_cmd then
+                    local oldir = os.cd(html_dir)
+                    os.execv(zip_cmd, {"-r", "-q", zip_path, "."})
+                    os.cd(oldir)
+                else
+                    raise("Unable to find a suitable zip tool (need 7z or zip)")
+                end
+            end
+        end
+    end)
+
     if is_plat("windows") then
         add_files("zen.rc")
         add_ldflags("/subsystem:console,5.02", {force = true})