Extension point so private/unsupported platforms can plug in their own implementations of the kernel/libc primitives Tracy depends on, without patching the `#if`/`#elif` chains.
Projects supply a platform header via `-DTRACY_PLATFORM_HEADER="\"my_platform.h\""` at build time. Tracy includes it in any TU that needs the hooks. The header toggles per-category `TRACY_HAS_CUSTOM_*` macros and declares matching `tracy::Platform*` functions.
Available hooks:
- `TRACY_HAS_CUSTOM_THREAD_ID` → `PlatformGetThreadId`
- `TRACY_HAS_CUSTOM_USER_INFO` → `PlatformGetHostname`, `PlatformGetUserLogin`, `PlatformGetUserFullName`
- `TRACY_HAS_CUSTOM_SAFE_COPY` → `PlatformSafeMemcpy`
- `TRACY_HAS_CUSTOM_ALLOCATOR` → `PlatformMalloc`, `PlatformFree`, `PlatformRealloc`, `PlatformAllocatorInit`, `PlatformAllocatorThreadInit`, `PlatformAllocatorFinalize`, `PlatformAllocatorThreadFinalize`
Each hook is wired as the first arm of its respective `#if`/`#elif` chain, so existing supported platforms are unaffected.
Template files in `examples/CustomPlatform/` and a new subsection in `manual/tracy.tex` document the mechanism.
The documentation states that Tracy is disabled by default, but the
build system defaults were ON/true. Change CMake and Meson defaults to
OFF/false. Projects that need profiling enabled must now opt in
explicitly. Add explicit TRACY_ENABLE=ON / tracy_enable=true to CI
steps and the test project to preserve existing behavior.
