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/session/identity.go

@@ -21,15 +21,16 @@ const (
 // AgentIdentity represents a parsed Gas Town agent identity.
 type AgentIdentity struct {
 	Role Role   // mayor, deacon, witness, refinery, crew, polecat
-	Rig  string // empty for mayor/deacon
+	Town string // town name (for mayor/deacon only)
+	Rig  string // rig name (empty for mayor/deacon)
 	Name string // crew/polecat name (empty for mayor/deacon/witness/refinery)
 }
 
 // ParseSessionName parses a tmux session name into an AgentIdentity.
 //
 // Session name formats:
-//   - gt-mayor → Role: mayor
-//   - gt-deacon → Role: deacon
+//   - gt-<town>-mayor → Role: mayor, Town: <town>
+//   - gt-<town>-deacon → Role: deacon, Town: <town>
 //   - gt-<rig>-witness → Role: witness, Rig: <rig>
 //   - gt-<rig>-refinery → Role: refinery, Rig: <rig>
 //   - gt-<rig>-crew-<name> → Role: crew, Rig: <rig>, Name: <name>
@@ -48,18 +49,20 @@ func ParseSessionName(session string) (*AgentIdentity, error) {
 		return nil, fmt.Errorf("invalid session name %q: empty after prefix", session)
 	}
 
-	// Check for global roles first (no rig)
-	switch suffix {
-	case "mayor":
-		return &AgentIdentity{Role: RoleMayor}, nil
-	case "deacon":
-		return &AgentIdentity{Role: RoleDeacon}, nil
-	}
-
-	// Parse rig-based roles
+	// Parse into parts
 	parts := strings.Split(suffix, "-")
 	if len(parts) < 2 {
-		return nil, fmt.Errorf("invalid session name %q: expected rig-role format", session)
+		return nil, fmt.Errorf("invalid session name %q: expected town-role or rig-role format", session)
+	}
+
+	// Check for mayor/deacon (town-level roles with suffix marker)
+	if parts[len(parts)-1] == "mayor" {
+		town := strings.Join(parts[:len(parts)-1], "-")
+		return &AgentIdentity{Role: RoleMayor, Town: town}, nil
+	}
+	if parts[len(parts)-1] == "deacon" {
+		town := strings.Join(parts[:len(parts)-1], "-")
+		return &AgentIdentity{Role: RoleDeacon, Town: town}, nil
 	}
 
 	// Check for witness/refinery (suffix markers)
@@ -94,9 +97,9 @@ func ParseSessionName(session string) (*AgentIdentity, error) {
 func (a *AgentIdentity) SessionName() string {
 	switch a.Role {
 	case RoleMayor:
-		return MayorSessionName()
+		return MayorSessionName(a.Town)
 	case RoleDeacon:
-		return DeaconSessionName()
+		return DeaconSessionName(a.Town)
 	case RoleWitness:
 		return WitnessSessionName(a.Rig)
 	case RoleRefinery: