fix: restore agent override support lost in manager refactors

The manager refactors (ea8bef2, 72544cc0) conflicted with the agent
override feature, causing regressions:

Deacon (ea8bef2):
- Lost agentOverride parameter
- Re-added respawn loop (removed in 5f2e16f)
- Lost GUPP (startup + propulsion nudges)

Crew (72544cc0):
- Lost agentOverride wiring to StartOptions
- --agent flag had no effect on crew refresh/restart

This fix restores agent override support and GUPP while keeping
improvements from the manager refactors (zombie detection, etc).

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

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

internal/cmd/up.go

@@ -83,7 +83,7 @@ func runUp(cmd *cobra.Command, args []string) error {
 
 	// 2. Deacon (Claude agent)
 	deaconMgr := deacon.NewManager(townRoot)
-	if err := deaconMgr.Start(); err != nil {
+	if err := deaconMgr.Start(""); err != nil {
 		if err == deacon.ErrAlreadyRunning {
 			printStatus("Deacon", true, deaconMgr.SessionName())
 		} else {