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, 251 insertions, 0 deletions

diff --git a/src/zen/trace/callstack_formatter.cpp b/src/zen/trace/callstack_formatter.cpp
new file mode 100644
index 000000000..0c601d5c0
--- /dev/null
+++ b/src/zen/trace/callstack_formatter.cpp
@@ -0,0 +1,251 @@
+// Copyright Epic Games, Inc. All Rights Reserved.
+
+#include "callstack_formatter.h"
+
+#include <zencore/fmtutils.h>
+#include <zencore/string.h>
+#include <zenutil/wildcard.h>
+
+#include <algorithm>
+
+namespace zen::trace_detail {
+
+namespace {
+
+	static bool IsKnownRuntimeModuleName(std::string_view ModuleName)
+	{
+		std::string LowerName = zen::ToLower(ModuleName);
+		return LowerName == "ntdll.dll" || LowerName == "kernel32.dll" || LowerName == "kernelbase.dll" || LowerName == "ucrtbase.dll" ||
+			   LowerName == "ucrtbased.dll" || LowerName.starts_with("vcruntime") || LowerName.starts_with("msvcp") ||
+			   LowerName.starts_with("api-ms-win-") || LowerName == "libc.so" || LowerName.starts_with("libc.so.") ||
+			   LowerName == "libstdc++.so" || LowerName.starts_with("libstdc++.so.") || LowerName == "libgcc_s.so" ||
+			   LowerName.starts_with("libgcc_s.so.") || LowerName == "libpthread.so" || LowerName.starts_with("libpthread.so.") ||
+			   LowerName == "libm.so" || LowerName.starts_with("libm.so.") || LowerName == "ld-linux.so" ||
+			   LowerName.starts_with("ld-linux") || LowerName == "libsystem_kernel.dylib" || LowerName == "libsystem_malloc.dylib" ||
+			   LowerName == "libsystem_pthread.dylib" || LowerName == "libdyld.dylib";
+	}
+
+	static bool PathLooksThirdParty(std::string_view ModulePath)
+	{
+		std::string LowerPath = zen::ToLower(ModulePath);
+		return LowerPath.find("/thirdparty/") != std::string::npos || LowerPath.find("\\thirdparty\\") != std::string::npos ||
+			   LowerPath.find("/third-party/") != std::string::npos || LowerPath.find("\\third-party\\") != std::string::npos ||
+			   LowerPath.find("/external/") != std::string::npos || LowerPath.find("\\external\\") != std::string::npos ||
+			   LowerPath.find("/extern/") != std::string::npos || LowerPath.find("\\extern\\") != std::string::npos ||
+			   LowerPath.find("/engine/binaries/thirdparty/") != std::string::npos ||
+			   LowerPath.find("\\engine\\binaries\\thirdparty\\") != std::string::npos ||
+			   LowerPath.find("c:\\windows\\system32\\") != std::string::npos ||
+			   LowerPath.find("c:\\windows\\syswow64\\") != std::string::npos || LowerPath.starts_with("/usr/lib/") ||
+			   LowerPath.starts_with("/lib/") || LowerPath.starts_with("/system/");
+	}
+
+	static bool MatchesAnyPattern(std::string_view Text, const std::vector<std::string>& Patterns)
+	{
+		for (const std::string& Pattern : Patterns)
+		{
+			if (zen::MatchWildcard(Pattern, Text, /*CaseSensitive=*/false))
+			{
+				return true;
+			}
+		}
+		return false;
+	}
+
+	static bool ShouldSkipFrameByPattern(const CallstackFilterOptions& Options,
+										 const TraceModel&			   Model,
+										 const ResolvedFrame&		   Frame,
+										 std::string_view			   Description)
+	{
+		if (MatchesAnyPattern(Description, Options.SkipPatterns))
+		{
+			return true;
+		}
+		if (Frame.ModuleIndex != ~0u && Frame.ModuleIndex < Model.Modules.size())
+		{
+			const ModuleInfo& Module = Model.Modules[Frame.ModuleIndex];
+			if (MatchesAnyPattern(Module.Name, Options.SkipPatterns) || MatchesAnyPattern(Module.FullPath, Options.SkipPatterns))
+			{
+				return true;
+			}
+		}
+
+		static const std::vector<std::string> kDefaultSkipPatterns = {
+			"zen::MemoryTrace_*",
+			"*mi_*",
+			"*_mi_*",
+			"*rpmalloc*",
+			"*mimalloc*",
+			"*je_malloc*",
+			"*je_free*",
+			"*malloc*",
+			"*free*",
+			"*realloc*",
+		};
+		return MatchesAnyPattern(Description, kDefaultSkipPatterns);
+	}
+
+	static bool IsThirdPartyFrame(const TraceModel& Model, const ResolvedFrame& Frame, std::string_view Description)
+	{
+		if (Description.starts_with("std::"))
+		{
+			return true;
+		}
+		if (Frame.ModuleIndex == ~0u || Frame.ModuleIndex >= Model.Modules.size())
+		{
+			return false;
+		}
+
+		const ModuleInfo& Module = Model.Modules[Frame.ModuleIndex];
+		return IsKnownRuntimeModuleName(Module.Name) || PathLooksThirdParty(Module.FullPath);
+	}
+
+}  // namespace
+
+CallstackFormatter::CallstackFormatter(const TraceModel& InModel, const SymbolResolver* InSymbols) : m_Model(InModel), m_Symbols(InSymbols)
+{
+}
+
+const CallstackEntry*
+CallstackFormatter::FindCallstackEntry(uint32_t CallstackId) const
+{
+	auto It =
+		eastl::lower_bound(m_Model.Callstacks.begin(), m_Model.Callstacks.end(), CallstackId, [](const CallstackEntry& E, uint32_t Id) {
+			return E.Id < Id;
+		});
+	if (It == m_Model.Callstacks.end() || It->Id != CallstackId)
+	{
+		return nullptr;
+	}
+	return &*It;
+}
+
+const std::string&
+CallstackFormatter::Describe(const ResolvedFrame& Frame)
+{
+	auto It = m_Cache.find(Frame.Address);
+	if (It != m_Cache.end())
+	{
+		return It->second;
+	}
+
+	std::string Result = m_Symbols ? m_Symbols->Resolve(Frame.Address) : std::string{};
+	if (Result.empty())
+	{
+		if (Frame.ModuleIndex != ~0u && Frame.ModuleIndex < m_Model.Modules.size())
+		{
+			Result = fmt::format("{} + 0x{:X}", m_Model.Modules[Frame.ModuleIndex].Name, Frame.Offset);
+		}
+		else
+		{
+			Result = fmt::format("0x{:X}", Frame.Address);
+		}
+	}
+
+	auto [InsertedIt, Inserted] = m_Cache.emplace(Frame.Address, std::move(Result));
+	ZEN_UNUSED(Inserted);
+	return InsertedIt->second;
+}
+
+FilteredCallstackView
+CallstackFormatter::BuildView(const CallstackEntry& Entry, const CallstackFilterOptions& Options)
+{
+	FilteredCallstackView Result;
+	Result.Frames.reserve(Entry.Frames.size());
+	if (Entry.Frames.empty())
+	{
+		return Result;
+	}
+
+	eastl::vector<bool> ExplicitSkip;
+	eastl::vector<bool> ThirdParty;
+	ExplicitSkip.reserve(Entry.Frames.size());
+	ThirdParty.reserve(Entry.Frames.size());
+
+	for (const ResolvedFrame& Frame : Entry.Frames)
+	{
+		const std::string& Description = Describe(Frame);
+		ExplicitSkip.push_back(ShouldSkipFrameByPattern(Options, m_Model, Frame, Description));
+		ThirdParty.push_back(IsThirdPartyFrame(m_Model, Frame, Description));
+	}
+
+	eastl::vector<size_t> VisibleFrameIndices;
+	VisibleFrameIndices.reserve(Entry.Frames.size());
+
+	if (!Options.EnableHeuristic)
+	{
+		for (size_t Index = 0; Index < Entry.Frames.size(); ++Index)
+		{
+			if (!ExplicitSkip[Index])
+			{
+				VisibleFrameIndices.push_back(Index);
+			}
+		}
+		if (VisibleFrameIndices.empty())
+		{
+			VisibleFrameIndices.push_back(0);
+		}
+	}
+	else
+	{
+		size_t FirstProgramIndex	   = Entry.Frames.size();
+		size_t BoundaryThirdPartyIndex = Entry.Frames.size();
+		for (size_t Index = 0; Index < Entry.Frames.size(); ++Index)
+		{
+			if (ExplicitSkip[Index])
+			{
+				continue;
+			}
+			if (ThirdParty[Index])
+			{
+				BoundaryThirdPartyIndex = Index;
+				continue;
+			}
+			FirstProgramIndex = Index;
+			break;
+		}
+
+		if (FirstProgramIndex == Entry.Frames.size())
+		{
+			for (size_t Index = 0; Index < Entry.Frames.size(); ++Index)
+			{
+				if (!ExplicitSkip[Index])
+				{
+					VisibleFrameIndices.push_back(Index);
+				}
+			}
+			if (VisibleFrameIndices.empty())
+			{
+				VisibleFrameIndices.push_back(0);
+			}
+		}
+		else
+		{
+			if (BoundaryThirdPartyIndex < Entry.Frames.size())
+			{
+				VisibleFrameIndices.push_back(BoundaryThirdPartyIndex);
+				Result.IncludedThirdPartyBoundary = true;
+			}
+			for (size_t Index = FirstProgramIndex; Index < Entry.Frames.size(); ++Index)
+			{
+				if (!ExplicitSkip[Index])
+				{
+					VisibleFrameIndices.push_back(Index);
+				}
+			}
+			if (VisibleFrameIndices.empty())
+			{
+				VisibleFrameIndices.push_back(FirstProgramIndex);
+			}
+		}
+	}
+
+	Result.HiddenPrefixCount = uint32_t(VisibleFrameIndices.front());
+	for (size_t FrameIndex : VisibleFrameIndices)
+	{
+		Result.Frames.push_back(
+			{.OriginalIndex = FrameIndex, .Frame = &Entry.Frames[FrameIndex], .Display = Describe(Entry.Frames[FrameIndex])});
+	}
+	return Result;
+}
+
+}  // namespace zen::trace_detail