[soltros]

The bake tool rejects capable compilers because its probe unconditionally declares a mutable static inside a constexpr function. Windows skeleton tests also rebuild the same translator three times, exceeding the source-suite timeout. This repairs compiler discovery and shares one translator cache within the skeleton-test process.

Related: #93; inherited failures observed in #109.

Compiler probing now models the actual conditional static-in-constexpr requirement and verifies a valid constant-expression path. It tries C++23/C++2b only, reports compiler errors, bounds each probe to 30 seconds, ignores the stale shared standard cache, and tries other discovered compilers when a preferred candidate lacks the feature. Explicit BAKE_CXX remains authoritative and fails visibly. Object-cache stamps now include compiler identity and are rewritten after invalidation.

The bake tests pass their preferred compiler through capability discovery. Skeleton tests declare compiler/header requirements to the suite runner and reuse one temporary translator directory across all three translation cases; their separate synthetic inputs and behavioral assertions remain intact.

Validation: four compiler-discovery regression cases pass (conditional probe, stale cache, candidate fallback, strict override). Standalone skeleton: 6 passed, 3 skipped because this host lacks the required translator toolchain/headers. Full local suite: 272 passed, 12 failed, 52 skipped; the additional explicit skip is the skeleton file's now-declared missing dependencies. No game data is used.

Final platform validation: these exact changes passed together in #114. Windows: 317 passed, 0 failed, 21 skipped; Linux: 329 passed, 0 failed, 9 skipped. Actual Mimo and skeleton translation tests passed on both platforms. Windows Builder, Linux AppImage, actionlint and both focused shader jobs also passed. Standalone branch failures were the separately repaired inherited defects; no checks were removed or disabled.