Remove the public allow_test_bootstrap production seam so caller-controlled
flags cannot forge native mutation provenance. Bind provenance to the resolved
canonical entrypoint path plus a live stdio transport bind; basename-only
mcp_server.py stack frames and import-only launch no longer authorize
mutations. Test-mode install_test_native_runtime is pytest-only and cannot
reach production Gitea mutation endpoints. Add AC9 regressions for both
reviewer-found bypasses and related spoof vectors.
Refs: PR #696 REQUEST_CHANGES at 253269c; issue #695 comments 11002/11005.