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, 166 insertions, 0 deletions

diff --git a/thirdparty/tourist/trace/src/data.cpp b/thirdparty/tourist/trace/src/data.cpp
new file mode 100644
index 000000000..da42284dc
--- /dev/null
+++ b/thirdparty/tourist/trace/src/data.cpp
@@ -0,0 +1,166 @@
+#include <foundation/platform.h>
+#include <foundation/types.h>
+#include <trace/detail/data.h>
+
+//------------------------------------------------------------------------------
+#ifdef _WIN32
+
+DataSource::DataSource(const Path& path)
+{
+    HANDLE handle = CreateFileW(path.c_str(), GENERIC_READ, FILE_SHARE_READ,
+        nullptr, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr);
+    if (handle == INVALID_HANDLE_VALUE)
+        throw std::runtime_error("Failed to open file");
+
+    _handle = uintptr(handle);
+}
+
+DataSource::~DataSource()
+{
+    auto handle = HANDLE(_handle);
+    CloseHandle(handle);
+}
+
+int32 DataSource::read(void* out, uint32 size)
+{
+    auto handle = HANDLE(_handle);
+
+    DWORD bytes_read;
+    if (!ReadFile(handle, out, size, &bytes_read, nullptr))
+        throw std::runtime_error("Read error");
+
+    return bytes_read;
+}
+
+int64 DataSource::get_size() const
+{
+    if (_size >= 0)
+        return _size;
+
+    auto handle = HANDLE(_handle);
+
+    LARGE_INTEGER out;
+    GetFileSizeEx(handle, &out);
+    return _size = out.QuadPart;
+}
+
+#else // POSIX
+
+DataSource::DataSource(const Path& path)
+{
+    int fd = ::open(path.string().c_str(), O_RDONLY);
+    if (fd < 0)
+        throw std::runtime_error("Failed to open file");
+
+    _handle = uintptr(fd);
+}
+
+DataSource::~DataSource()
+{
+    ::close(int(_handle));
+}
+
+int32 DataSource::read(void* out, uint32 size)
+{
+    ssize_t bytes_read = ::read(int(_handle), out, size);
+    if (bytes_read < 0)
+        throw std::runtime_error("Read error");
+
+    return int32(bytes_read);
+}
+
+int64 DataSource::get_size() const
+{
+    if (_size >= 0)
+        return _size;
+
+    struct stat st;
+    if (fstat(int(_handle), &st) < 0)
+        return _size = 0;
+
+    return _size = st.st_size;
+}
+
+#endif
+
+
+
+//------------------------------------------------------------------------------
+DataStream::DataStream(DataSource& data_source, Allocator& allocator)
+: _data_source(data_source)
+, _allocator(allocator)
+{
+}
+
+//------------------------------------------------------------------------------
+uint64 DataStream::tell() const
+{
+    return _position;
+}
+
+//------------------------------------------------------------------------------
+uint32 DataStream::get_available() const
+{
+    return _stream.get_remaining();
+}
+
+//------------------------------------------------------------------------------
+Buffer DataStream::read(uint32 size)
+{
+    const uint8* ptr = _read(size);
+    return _buffer.create_sub_buffer(ptr, size);
+}
+
+//------------------------------------------------------------------------------
+const uint8* DataStream::_read(uint32 size)
+{
+    _position += size;
+
+    if (_stream.get_remaining() >= size)
+        return _stream.read(size);
+
+    MutableBuffer buffer = _allocator.create_buffer(BUFFER_SIZE);
+    uint8* cursor = buffer.get_pointer();
+    uint32 buffer_size = buffer.get_size();
+
+    if (uint32 remaining = _stream.get_remaining())
+    {
+        const void* src = _stream.read(remaining);
+        std::memcpy(cursor, src, remaining);
+        cursor += remaining;
+        buffer_size -= remaining;
+    }
+
+    uint32 read_size = 0;
+    while (true)
+    {
+        int32 i = _data_source.read(cursor + read_size, buffer_size - read_size);
+        if (i <= 0)
+            throw Eof();
+
+        if ((read_size += i) >= size)
+            break;
+    }
+
+    if (read_size < buffer_size)
+    {
+        buffer_size = BUFFER_SIZE - buffer_size + read_size;
+        _buffer = buffer.create_sub_buffer(0u, buffer_size);
+    }
+    else
+        _buffer = std::move(buffer);
+
+    _stream = _buffer.create_stream();
+
+    return _stream.read(size);
+}
+
+//------------------------------------------------------------------------------
+template <>  int8  DataStream::read< int8 >() { return *( int8 *)_read(sizeof( int8 )); }
+template <>  int16 DataStream::read< int16>() { return *( int16*)_read(sizeof( int16)); }
+template <>  int32 DataStream::read< int32>() { return *( int32*)_read(sizeof( int32)); }
+template <>  int64 DataStream::read< int64>() { return *( int64*)_read(sizeof( int64)); }
+template <> uint8  DataStream::read<uint8 >() { return *(uint8 *)_read(sizeof(uint8 )); }
+template <> uint16 DataStream::read<uint16>() { return *(uint16*)_read(sizeof(uint16)); }
+template <> uint32 DataStream::read<uint32>() { return *(uint32*)_read(sizeof(uint32)); }
+template <> uint64 DataStream::read<uint64>() { return *(uint64*)_read(sizeof(uint64)); }