feat(tmux): add per-rig color themes and dynamic status line (gt-vc1n)

Add tmux status bar theming for Gas Town sessions:

- Per-rig color themes auto-assigned via consistent hashing
- 10 curated dark themes (ocean, forest, rust, plum, etc.)
- Special gold/dark theme for Mayor
- Dynamic status line showing current issue and mail count
- Mayor status shows polecat/rig counts

New commands:
- gt theme --list: show available themes
- gt theme apply: apply to running sessions
- gt issue set/clear: agents update their current issue
- gt status-line: internal command for tmux refresh

Status bar format:
- Left: [rig/worker] role
- Right: <issue> | <mail> | HH:MM

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

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

internal/cmd/theme.go

@@ -0,0 +1,193 @@
+package cmd
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/spf13/cobra"
+	"github.com/steveyegge/gastown/internal/tmux"
+)
+
+var (
+	themeListFlag  bool
+	themeApplyFlag bool
+)
+
+var themeCmd = &cobra.Command{
+	Use:   "theme [name]",
+	Short: "View or set tmux theme for the current rig",
+	Long: `Manage tmux status bar themes for Gas Town sessions.
+
+Without arguments, shows the current theme assignment.
+With a name argument, sets the theme for this rig.
+
+Examples:
+  gt theme              # Show current theme
+  gt theme --list       # List available themes
+  gt theme forest       # Set theme to 'forest'
+  gt theme apply        # Apply theme to all running sessions in this rig`,
+	RunE: runTheme,
+}
+
+var themeApplyCmd = &cobra.Command{
+	Use:   "apply",
+	Short: "Apply theme to all running sessions in this rig",
+	RunE:  runThemeApply,
+}
+
+func init() {
+	rootCmd.AddCommand(themeCmd)
+	themeCmd.AddCommand(themeApplyCmd)
+	themeCmd.Flags().BoolVarP(&themeListFlag, "list", "l", false, "List available themes")
+}
+
+func runTheme(cmd *cobra.Command, args []string) error {
+	// List mode
+	if themeListFlag {
+		fmt.Println("Available themes:")
+		for _, name := range tmux.ListThemeNames() {
+			theme := tmux.GetThemeByName(name)
+			fmt.Printf("  %-10s  %s\n", name, theme.Style())
+		}
+		// Also show Mayor theme
+		mayor := tmux.MayorTheme()
+		fmt.Printf("  %-10s  %s (Mayor only)\n", mayor.Name, mayor.Style())
+		return nil
+	}
+
+	// Determine current rig
+	rigName := detectCurrentRig()
+	if rigName == "" {
+		rigName = "unknown"
+	}
+
+	// Show current theme assignment
+	if len(args) == 0 {
+		theme := tmux.AssignTheme(rigName)
+		fmt.Printf("Rig: %s\n", rigName)
+		fmt.Printf("Theme: %s (%s)\n", theme.Name, theme.Style())
+		return nil
+	}
+
+	// Set theme
+	themeName := args[0]
+	theme := tmux.GetThemeByName(themeName)
+	if theme == nil {
+		return fmt.Errorf("unknown theme: %s (use --list to see available themes)", themeName)
+	}
+
+	// TODO: Save to rig config.json
+	fmt.Printf("Theme '%s' selected for rig '%s'\n", themeName, rigName)
+	fmt.Println("Note: Run 'gt theme apply' to apply to running sessions")
+	fmt.Println("(Persistent config not yet implemented)")
+
+	return nil
+}
+
+func runThemeApply(cmd *cobra.Command, args []string) error {
+	t := tmux.NewTmux()
+
+	// Get all sessions
+	sessions, err := t.ListSessions()
+	if err != nil {
+		return fmt.Errorf("listing sessions: %w", err)
+	}
+
+	// Determine current rig
+	rigName := detectCurrentRig()
+
+	// Apply to matching sessions
+	applied := 0
+	for _, session := range sessions {
+		if !strings.HasPrefix(session, "gt-") {
+			continue
+		}
+
+		// Determine theme and identity for this session
+		var theme tmux.Theme
+		var rig, worker, role string
+
+		if session == "gt-mayor" {
+			theme = tmux.MayorTheme()
+			worker = "Mayor"
+			role = "coordinator"
+		} else {
+			// Parse session name: gt-<rig>-<worker> or gt-<rig>-crew-<name>
+			parts := strings.SplitN(session, "-", 3)
+			if len(parts) < 3 {
+				continue
+			}
+			rig = parts[1]
+
+			// Skip if not matching current rig (if we know it)
+			if rigName != "" && rig != rigName {
+				continue
+			}
+
+			workerPart := parts[2]
+			if strings.HasPrefix(workerPart, "crew-") {
+				worker = strings.TrimPrefix(workerPart, "crew-")
+				role = "crew"
+			} else {
+				worker = workerPart
+				role = "polecat"
+			}
+
+			theme = tmux.AssignTheme(rig)
+		}
+
+		// Apply theme and status format
+		if err := t.ApplyTheme(session, theme); err != nil {
+			fmt.Printf("  %s: failed (%v)\n", session, err)
+			continue
+		}
+		if err := t.SetStatusFormat(session, rig, worker, role); err != nil {
+			fmt.Printf("  %s: failed to set format (%v)\n", session, err)
+			continue
+		}
+		if err := t.SetDynamicStatus(session); err != nil {
+			fmt.Printf("  %s: failed to set dynamic status (%v)\n", session, err)
+			continue
+		}
+
+		fmt.Printf("  %s: applied %s theme\n", session, theme.Name)
+		applied++
+	}
+
+	if applied == 0 {
+		fmt.Println("No matching sessions found")
+	} else {
+		fmt.Printf("\nApplied theme to %d session(s)\n", applied)
+	}
+
+	return nil
+}
+
+// detectCurrentRig determines the rig from environment or cwd.
+func detectCurrentRig() string {
+	// Try environment first
+	if rig := detectCurrentSession(); rig != "" {
+		// Extract rig from session name
+		parts := strings.SplitN(rig, "-", 3)
+		if len(parts) >= 2 && parts[0] == "gt" {
+			return parts[1]
+		}
+	}
+
+	// Try to detect from cwd
+	cwd, err := findBeadsWorkDir()
+	if err != nil {
+		return ""
+	}
+
+	// Extract rig name from path
+	// Typical paths: /Users/stevey/gt/<rig>/...
+	parts := strings.Split(cwd, "/")
+	for i, p := range parts {
+		if p == "gt" && i+1 < len(parts) {
+			return parts[i+1]
+		}
+	}
+
+	return ""
+}