Revert to simple gt-mayor/gt-deacon session names

Reverts the session naming changes from PR #70. Multi-town support
on a single machine is not a real use case - rigs provide project
isolation, and true isolation should use containers/VMs.

Changes:
- MayorSessionName() and DeaconSessionName() no longer take townName parameter
- ParseSessionName() handles simple gt-mayor and gt-deacon formats
- Removed Town field from AgentIdentity and AgentSession structs
- Updated all callers and tests

Generated with Claude Code

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

internal/cmd/theme.go

@@ -117,15 +117,9 @@ func runThemeApply(cmd *cobra.Command, args []string) error {
 	// Determine current rig
 	rigName := detectCurrentRig()
 
-	// Get town name for session name comparison
-	var mayorSession, deaconSession string
-	townRoot, err := workspace.FindFromCwd()
-	if err == nil && townRoot != "" {
-		if townName, err := workspace.GetTownName(townRoot); err == nil {
-			mayorSession = session.MayorSessionName(townName)
-			deaconSession = session.DeaconSessionName(townName)
-		}
-	}
+	// Get session names for comparison
+	mayorSession := session.MayorSessionName()
+	deaconSession := session.DeaconSessionName()
 
 	// Apply to matching sessions
 	applied := 0