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>

internal/cmd/doctor.go

@@ -85,8 +85,8 @@ func runDoctor(cmd *cobra.Command, args []string) error {
 	d.Register(doctor.NewPatrolPluginsAccessibleCheck())
 	d.Register(doctor.NewPatrolRolesHavePromptsCheck())
 
-	// Attachment checks
-	d.Register(doctor.NewStaleAttachmentsCheck())
+	// NOTE: StaleAttachmentsCheck removed - staleness detection belongs in Deacon molecule
+	// See gt-gaxo epic for ZFC cleanup rationale
 
 	// Config architecture checks
 	d.Register(doctor.NewSettingsCheck())