refactor: ZFC cleanup - move Go heuristics to Deacon molecule (gt-gaxo)

Remove Go code that makes workflow decisions. All health checking,
staleness detection, nudging, and escalation belongs in the Deacon
molecule where Claude executes it.

Removed:
- internal/daemon/backoff.go (190 lines) - exponential backoff decisions
- internal/doctor/stale_check.go (284 lines) - staleness detection
- IsFresh/IsStale/IsVeryStale from keepalive.go
- pokeMayor, pokeWitnesses, pokeWitness from daemon.go
- Heartbeat staleness classification from pokeDeacon

Changed:
- Lifecycle parsing now uses structured body (JSON or simple text)
  instead of keyword matching on subject line
- Daemon now only ensures Deacon is running and sends simple heartbeats
- No backoff, no staleness classification, no decision-making

Total: ~800 lines removed from Go code

The Deacon molecule will handle all health checking, nudging, and
escalation. Go is now just a message router.

See gt-gaxo epic for full rationale.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

AGENTS.md

@@ -3,3 +3,29 @@
 See **CLAUDE.md** for complete agent context and instructions.
 
 This file exists for compatibility with tools that look for AGENTS.md.
+
+## Landing the Plane (Session Completion)
+
+**When ending a work session**, you MUST complete ALL steps below. Work is NOT complete until `git push` succeeds.
+
+**MANDATORY WORKFLOW:**
+
+1. **File issues for remaining work** - Create issues for anything that needs follow-up
+2. **Run quality gates** (if code changed) - Tests, linters, builds
+3. **Update issue status** - Close finished work, update in-progress items
+4. **PUSH TO REMOTE** - This is MANDATORY:
+   ```bash
+   git pull --rebase
+   bd sync
+   git push
+   git status  # MUST show "up to date with origin"
+   ```
+5. **Clean up** - Clear stashes, prune remote branches
+6. **Verify** - All changes committed AND pushed
+7. **Hand off** - Provide context for next session
+
+**CRITICAL RULES:**
+- Work is NOT complete until `git push` succeeds
+- NEVER stop before pushing - that leaves work stranded locally
+- NEVER say "ready to push when you are" - YOU must push
+- If push fails, resolve and retry until it succeeds