ci(windows): run the local-symbol probes from the archive build
Draft measurement PR: Windows shard 1 runs the local-symbol backtrace probes from the archive build instead of cold-compiling a separate debug build. Timings collected for review; not for merge as-is (the enablement commit is temporary).
Summary by cubic
Runs the Windows local-symbol backtrace probes from the archive build's already-linked library harness instead of cold-compiling a separate debug build on shard one. Probes execute directly against the exact library binary named in the archive's metadata instead of through cargo test, which a native run showed recompiles the library anyway (5m24 after the 6m09 archive build); Python 3.14 streams the zstd archive metadata without extracting binaries, preserving the linked harness and its local PDB. Every Windows libtest shard now runs only archive-backed hash partitions.
- Adds
scripts/ci-windows-probes.pywith libtest inventory checking, exactly-once execution, and child-status propagation, covered by 11 unit tests plus workflow ownership and gate-collection regressions.