Remove shell respawn loops from witness and deacon

Currently witness and deacon use shell loops (`while true; do claude; done`) to auto-respawn when Claude exits. This bypasses the proper lifecycle architecture.

## Current Behavior
- witness.go: ensureWitnessSession() wraps Claude in a shell loop
- deacon.go: runDeaconStart() wraps Claude in a shell loop
- When Claude exits, shell automatically restarts it

## Desired Behavior
- Agents should request lifecycle changes via LIFECYCLE mail to deacon
- Daemon processes lifecycle requests and handles restarts
- No shell loops - daemon and deacon's health-scan handle respawns

## Why Change
1. Shell loops bypass state verification (requesting_cycle flag)
2. Shell loops bypass handoff mail protocol
3. Shell loops make lifecycle tracking harder
4. Daemon already has infrastructure for this

## Migration
1. Remove shell loop from witness (daemon/deacon handles restart)
2. Remove shell loop from deacon (daemon handles restart via ensureDeaconRunning)
3. Verify daemon's health check properly restarts dead agents
4. Update templates if needed

## Risk
Low - we have gt witness restart and gt deacon restart as fallbacks

Removed shell respawn loops from witness and deacon. Daemon now properly detects dead Claude via pane command and restarts.