feat(account): add gt account switch command

Adds the ability to switch between Claude Code accounts with a single command:
  gt account switch <handle>

The command:
1. Detects current account by checking ~/.claude symlink target
2. If ~/.claude is a real directory, moves it to the current account config_dir
3. Removes existing ~/.claude symlink (if any)
4. Creates symlink from ~/.claude to target account config_dir
5. Updates default account in accounts.json
6. Prints confirmation with restart reminder

Handles edge cases:
- Already on target account (no-op with message)
- Target account does not exist (error with list of valid accounts)
- ~/.claude is real directory (first-time setup scenario)

Closes gt-jd8m1

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

internal/cmd/account.go

@@ -264,6 +264,25 @@ Examples:
 	RunE: runAccountStatus,
 }
 
+var accountSwitchCmd = &cobra.Command{
+	Use:   "switch <handle>",
+	Short: "Switch to a different account",
+	Long: `Switch the active Claude Code account.
+
+This command:
+1. Backs up ~/.claude to the current account's config_dir (if needed)
+2. Creates a symlink from ~/.claude to the target account's config_dir
+3. Updates the default account in accounts.json
+
+After switching, you must restart Claude Code for the change to take effect.
+
+Examples:
+  gt account switch work       # Switch to work account
+  gt account switch personal   # Switch to personal account`,
+	Args: cobra.ExactArgs(1),
+	RunE: runAccountSwitch,
+}
+
 func runAccountStatus(cmd *cobra.Command, args []string) error {
 	townRoot, err := workspace.FindFromCwd()
 	if err != nil {
@@ -318,6 +337,122 @@ func runAccountStatus(cmd *cobra.Command, args []string) error {
 	return nil
 }
 
+func runAccountSwitch(cmd *cobra.Command, args []string) error {
+	targetHandle := args[0]
+
+	townRoot, err := workspace.FindFromCwd()
+	if err != nil {
+		return fmt.Errorf("finding town root: %w", err)
+	}
+
+	accountsPath := constants.MayorAccountsPath(townRoot)
+	cfg, err := config.LoadAccountsConfig(accountsPath)
+	if err != nil {
+		return fmt.Errorf("loading accounts config: %w", err)
+	}
+
+	// Check if target account exists
+	targetAcct := cfg.GetAccount(targetHandle)
+	if targetAcct == nil {
+		// List available accounts
+		var handles []string
+		for h := range cfg.Accounts {
+			handles = append(handles, h)
+		}
+		sort.Strings(handles)
+		return fmt.Errorf("account '%s' not found. Available accounts: %v", targetHandle, handles)
+	}
+
+	// Get ~/.claude path
+	home, err := os.UserHomeDir()
+	if err != nil {
+		return fmt.Errorf("getting home directory: %w", err)
+	}
+	claudeDir := home + "/.claude"
+
+	// Check current state of ~/.claude
+	fileInfo, err := os.Lstat(claudeDir)
+	if err != nil && !os.IsNotExist(err) {
+		return fmt.Errorf("checking ~/.claude: %w", err)
+	}
+
+	// Determine current account (if any) by checking symlink target
+	var currentHandle string
+	if err == nil && fileInfo.Mode()&os.ModeSymlink != 0 {
+		// It's a symlink - find which account it points to
+		linkTarget, err := os.Readlink(claudeDir)
+		if err != nil {
+			return fmt.Errorf("reading symlink: %w", err)
+		}
+		for h, acct := range cfg.Accounts {
+			if acct.ConfigDir == linkTarget {
+				currentHandle = h
+				break
+			}
+		}
+	}
+
+	// Check if already on target account
+	if currentHandle == targetHandle {
+		fmt.Printf("Already on account '%s'\n", targetHandle)
+		return nil
+	}
+
+	// Handle the case where ~/.claude is a real directory (not a symlink)
+	if err == nil && fileInfo.Mode()&os.ModeSymlink == 0 && fileInfo.IsDir() {
+		// It's a real directory - need to move it
+		// Try to find which account it belongs to based on default
+		if currentHandle == "" && cfg.Default != "" {
+			currentHandle = cfg.Default
+		}
+
+		if currentHandle != "" {
+			currentAcct := cfg.GetAccount(currentHandle)
+			if currentAcct != nil {
+				// Move ~/.claude to the current account's config_dir
+				fmt.Printf("Moving ~/.claude to %s...\n", currentAcct.ConfigDir)
+
+				// Remove the target config dir if it exists (it might be empty from account add)
+				if _, err := os.Stat(currentAcct.ConfigDir); err == nil {
+					if err := os.RemoveAll(currentAcct.ConfigDir); err != nil {
+						return fmt.Errorf("removing existing config dir: %w", err)
+					}
+				}
+
+				if err := os.Rename(claudeDir, currentAcct.ConfigDir); err != nil {
+					return fmt.Errorf("moving ~/.claude to %s: %w", currentAcct.ConfigDir, err)
+				}
+			}
+		} else {
+			return fmt.Errorf("~/.claude is a directory but no default account is set. Please set a default account first with 'gt account default <handle>'")
+		}
+	} else if err == nil && fileInfo.Mode()&os.ModeSymlink != 0 {
+		// It's a symlink - remove it so we can create a new one
+		if err := os.Remove(claudeDir); err != nil {
+			return fmt.Errorf("removing existing symlink: %w", err)
+		}
+	}
+	// If ~/.claude doesn't exist, that's fine - we'll create the symlink
+
+	// Create symlink to target account
+	if err := os.Symlink(targetAcct.ConfigDir, claudeDir); err != nil {
+		return fmt.Errorf("creating symlink to %s: %w", targetAcct.ConfigDir, err)
+	}
+
+	// Update default account
+	cfg.Default = targetHandle
+	if err := config.SaveAccountsConfig(accountsPath, cfg); err != nil {
+		return fmt.Errorf("saving accounts config: %w", err)
+	}
+
+	fmt.Printf("Switched to account '%s'\n", targetHandle)
+	fmt.Printf("~/.claude -> %s\n", targetAcct.ConfigDir)
+	fmt.Println()
+	fmt.Println(style.Warning.Render("⚠️  Restart Claude Code for the change to take effect"))
+
+	return nil
+}
+
 func init() {
 	// Add flags
 	accountListCmd.Flags().BoolVar(&accountJSON, "json", false, "Output as JSON")
@@ -330,6 +465,7 @@ func init() {
 	accountCmd.AddCommand(accountAddCmd)
 	accountCmd.AddCommand(accountDefaultCmd)
 	accountCmd.AddCommand(accountStatusCmd)
+	accountCmd.AddCommand(accountSwitchCmd)
 
 	rootCmd.AddCommand(accountCmd)
 }