[CBEPX]

Session-start and prompt hooks now bound Git discovery and stale-job identity probes to the host deadline. Malformed or oversized input fails open, unread results survive failed parent delivery, and late progress cannot overwrite terminal state. Update collaboration instructions and fork metadata for 1.7.6.

Stabilize the #57 MCP fixture by installing its SIGTERM handler before writing its PID and allowing one second for startup. This test-only backport does not change the release package.

Validation at 5171964:

• npm run check: 1005 unit, 120 integration, and 24 Codex E2E tests pass.
• npm run test:coverage: 1149/1149 pass; 92.88% lines/statements, 84.16% branches, 97.82% functions.
• Real Fable 5.1 task from the exact archive returns the expected marker, with no fallback, failure, or touched files.
• Packed hook checks pass, including stalled identity deadlines and malformed/oversized payloads.
• Independent review of the combined release range found no blocking issues. One inherited minor remains: a fractional timeout can defer stale-job cleanup.

The archive contains 93 files, all byte-matched to source. Opus 5.5/Fable 5.1 runtime adaptation and exec-stable macOS cancellation remain in 1.7.7.