Add persistent theme config and fix crew session theming

- Fix crew sessions missing theme application (ConfigureGasTownSession)
- Add theme persistence to .gastown/config.json
- gt theme <name> now saves to config
- gt theme apply reads from config, falls back to hash-based default
- Improve rig detection using GT_RIG env var and path parsing
- gt theme shows whether theme is configured or default

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

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

internal/cmd/crew.go

@@ -506,6 +506,10 @@ func runCrewAt(cmd *cobra.Command, args []string) error {
 		_ = t.SetEnvironment(sessionID, "GT_RIG", r.Name)
 		_ = t.SetEnvironment(sessionID, "GT_CREW", name)
 
+		// Apply rig-based theming (uses config if set, falls back to hash)
+		theme := getThemeForRig(r.Name)
+		_ = t.ConfigureGasTownSession(sessionID, theme, r.Name, name, "crew")
+
 		// Wait for shell to be ready after session creation
 		if err := t.WaitForShellReady(sessionID, 5*time.Second); err != nil {
 			return fmt.Errorf("waiting for shell: %w", err)
@@ -847,6 +851,10 @@ func runCrewRestart(cmd *cobra.Command, args []string) error {
 	t.SetEnvironment(sessionID, "GT_RIG", r.Name)
 	t.SetEnvironment(sessionID, "GT_CREW", name)
 
+	// Apply rig-based theming (uses config if set, falls back to hash)
+	theme := getThemeForRig(r.Name)
+	_ = t.ConfigureGasTownSession(sessionID, theme, r.Name, name, "crew")
+
 	// Wait for shell to be ready
 	if err := t.WaitForShellReady(sessionID, 5*time.Second); err != nil {
 		return fmt.Errorf("waiting for shell: %w", err)