fix: Make Mayor/Deacon session names include town name

Session names `gt-mayor` and `gt-deacon` were hardcoded, causing tmux
session name collisions when running multiple towns simultaneously.

Changed to `gt-{town}-mayor` and `gt-{town}-deacon` format (e.g.,
`gt-ai-mayor`) to allow concurrent multi-town operation.

Key changes:
- session.MayorSessionName() and DeaconSessionName() now take townName param
- Added workspace.GetTownName() helper to load town name from config
- Updated all callers in cmd/, daemon/, doctor/, mail/, rig/, templates/
- Updated tests with new session name format
- Bead IDs remain unchanged (already scoped by .beads/ directory)

Fixes #60

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

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

internal/cmd/agents.go

@@ -35,6 +35,7 @@ type AgentSession struct {
 	Type      AgentType
 	Rig       string // For rig-specific agents
 	AgentName string // e.g., crew name, polecat name
+	Town      string // For mayor/deacon only (town name from session)
 }
 
 // AgentTypeColors maps agent types to tmux color codes.
@@ -135,13 +136,16 @@ func categorizeSession(name string) *AgentSession {
 	session := &AgentSession{Name: name}
 	suffix := strings.TrimPrefix(name, "gt-")
 
-	// Town-level agents
-	if suffix == "mayor" {
+	// Town-level agents: gt-{town}-mayor, gt-{town}-deacon
+	// Check if suffix ends with -mayor or -deacon (new format)
+	if strings.HasSuffix(suffix, "-mayor") {
 		session.Type = AgentMayor
+		session.Town = strings.TrimSuffix(suffix, "-mayor")
 		return session
 	}
-	if suffix == "deacon" {
+	if strings.HasSuffix(suffix, "-deacon") {
 		session.Type = AgentDeacon
+		session.Town = strings.TrimSuffix(suffix, "-deacon")
 		return session
 	}