snapshot: preserve the uncommitted Canary instrumentation (not authored here)

Working-tree snapshot taken 2026-07-28 so this work is not lost. To be clear
about provenance: NONE of this was written in the session that committed it —
it is pre-existing uncommitted work on phase-a-tracing, last committed 2026-07-09,
from the xenia-rs decoder/deadlock investigation. It is recorded verbatim, not
reviewed and not tested.

Contents: 24 tracked modifications (ppc_emit_memory, xex_module, object_table,
shim_utils, xboxkrnl threading/rtl, xevent/xobject/xthread, memory) plus the
untracked probe sources audit_68_host_mem_watch, audit_69_event_signal_watch,
audit_70_semaphore_release_watch, phase_b_snapshot, and cmake/toolchains.

Deliberately excluded: build-cross/ (51 GB of build output) and
vkd3d-proton.cache. Note third_party/snappy is a submodule pointer change whose
target may not be pushed anywhere, so this branch is a preservation record rather
than a guaranteed-buildable tree.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

third_party/CMakeLists.txt

@@ -332,12 +332,11 @@ else()
     X86_AVX512VNNI
     WITH_GZFILEOP
   )
-  if(NOT MSVC)
-    # GCC/Clang have native __builtin_ctz/__builtin_ctzll (MSVC gets these
-    # from fallback_builtins.h). Defining these enables optimized compare256
-    # and longest_match codepaths.
+  # Real cl.exe exposes all intrinsics unconditionally; GCC, Clang, AND clang-cl
+  # all need per-file -m<isa> flags to declare them. CMAKE_CXX_COMPILER_ID is
+  # "Clang" for both Linux Clang and clang-cl.
+  if(NOT MSVC OR CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
     target_compile_definitions(zlib-ng PRIVATE HAVE_BUILTIN_CTZ HAVE_BUILTIN_CTZLL)
-    # GCC/Clang need per-file ISA flags; MSVC handles this via runtime dispatch
     set_source_files_properties(
       zlib-ng/arch/x86/adler32_avx2.c
       zlib-ng/arch/x86/chunkset_avx2.c