fix: harden SessionEnd cleanup within Codex deadline

[CBEPX]

Summary

• keep SessionEnd inside the Codex 3-second hook cap with an internal deadline and recovery marker
• make cleanup two-phase so queued/running jobs become recoverable before process termination
• bound workspace and process identity probes, preserve safe manual cleanup handles, and recover pending cleanup on SessionStart
• release as 1.5.3

Verification

• npm run check: 715 unit, 73 integration, 22 E2E
• state mutation target: 57.39% (threshold 55%)
• render mutation shard: 61.85% (threshold 55%)
• process mutation target: 78.20% (threshold 55%)
• Claude Opus review findings resolved before final verification