Unify agent startup with Manager pattern

Refactors all agent startup paths (witness, refinery, crew, polecat) to use
a consistent Manager interface with Start(), Stop(), IsRunning(), and
SessionName() methods.

Includes:
- Witness manager with GUPP propulsion nudge for startup
- Refinery manager for engineer sessions
- Crew manager for worker agents
- Session/polecat manager updates
- claude_settings_check doctor check for settings validation
- Settings management consolidated from rig/manager.go
- Settings location moved outside source repos to prevent conflicts

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

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

internal/daemon/daemon.go

@@ -400,7 +400,7 @@ func (d *Daemon) ensureWitnessesRunning() {
 // ensureWitnessRunning ensures the witness for a specific rig is running.
 // Discover, don't track: uses Manager.Start() which checks tmux directly (gt-zecmc).
 func (d *Daemon) ensureWitnessRunning(rigName string) {
-// Check rig operational state before auto-starting
+	// Check rig operational state before auto-starting
 	if operational, reason := d.isRigOperational(rigName); !operational {
 		d.logger.Printf("Skipping witness auto-start for %s: %s", rigName, reason)
 		return