fix(stale): enable stale binary warning and fix source detection

- Add checkStaleBinaryWarning() call to persistentPreRun (was only in
  deprecated function)
- Fix GetRepoRoot() to look in correct location ($GT_ROOT/gastown/mayor/rig)
- Use hasGtSource() with os.Stat instead of shell test command

Agents will now see warnings when running gt with a stale binary.

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

internal/cmd/root.go

@@ -69,6 +69,11 @@ func persistentPreRun(cmd *cobra.Command, args []string) error {
 	// Get the root command name being run
 	cmdName := cmd.Name()
 
+	// Check for stale binary (warning only, doesn't block)
+	if !beadsExemptCommands[cmdName] {
+		checkStaleBinaryWarning()
+	}
+
 	// Check town root branch (warning only, non-blocking)
 	if !branchCheckExemptCommands[cmdName] {
 		warnIfTownRootOffMain()

internal/version/stale.go

@@ -107,12 +107,13 @@ func CheckStaleBinary(repoDir string) *StaleBinaryInfo {
 }
 
 // GetRepoRoot returns the git repository root for the gt source code.
-// It looks for the gastown repo by checking known paths.
+// The gt source lives in the gastown rig at $GT_ROOT/gastown/mayor/rig.
 func GetRepoRoot() (string, error) {
-	// First, check if GT_ROOT environment variable is set
+	// Check if GT_ROOT environment variable is set (agents always have this)
 	if gtRoot := os.Getenv("GT_ROOT"); gtRoot != "" {
-		if isGitRepo(gtRoot) && hasGastownMarker(gtRoot) {
+		rigPath := gtRoot + "/gastown/mayor/rig"
-			return gtRoot, nil
+		if hasGtSource(rigPath) {
+			return rigPath, nil
 		}
 	}
 
@@ -120,23 +121,22 @@ func GetRepoRoot() (string, error) {
 	home := os.Getenv("HOME")
 	if home != "" {
 		candidates := []string{
-			home + "/gt/gastown",
+			home + "/gt/gastown/mayor/rig",
-			home + "/gastown",
+			home + "/gastown/mayor/rig",
-			home + "/src/gastown",
+			home + "/src/gastown/mayor/rig",
-			home + "/dev/gastown",
 		}
 		for _, candidate := range candidates {
-			if isGitRepo(candidate) && hasGastownMarker(candidate) {
+			if hasGtSource(candidate) {
 				return candidate, nil
 			}
 		}
 	}
 
-	// Check if current directory is in a gastown repo
+	// Check if current directory is in the gt source repo
 	cmd := exec.Command("git", "rev-parse", "--show-toplevel")
 	if output, err := cmd.Output(); err == nil {
 		root := strings.TrimSpace(string(output))
-		if hasGastownMarker(root) {
+		if hasGtSource(root) {
 			return root, nil
 		}
 	}
@@ -151,11 +151,11 @@ func isGitRepo(dir string) bool {
 	return cmd.Run() == nil
 }
 
-// hasGastownMarker checks if a directory looks like the gastown repo.
+// hasGtSource checks if a directory contains the gt source code.
-func hasGastownMarker(dir string) bool {
+// We look for cmd/gt/main.go as the definitive marker.
-	// Check for cmd/gt directory which is unique to gastown
+func hasGtSource(dir string) bool {
-	cmd := exec.Command("test", "-d", dir+"/cmd/gt")
+	_, err := os.Stat(dir + "/cmd/gt/main.go")
-	return cmd.Run() == nil
+	return err == nil
 }
 
 // SetCommit allows the cmd package to pass in the build-time commit.