feat(doctor): add town-git check for version control

Checks whether the town root (~/gt) is under git version control.
Having the town harness in git is optional but recommended for:
- Backing up personal Gas Town configuration and history
- Tracking mail and coordination beads
- Easier federation across machines

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

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

internal/cmd/doctor.go

@@ -53,6 +53,7 @@ func runDoctor(cmd *cobra.Command, args []string) error {
 	d := doctor.NewDoctor()
 
 	// Register built-in checks
+	d.Register(doctor.NewTownGitCheck())
 	d.Register(doctor.NewDaemonCheck())
 	d.Register(doctor.NewBeadsDatabaseCheck())
 	d.Register(doctor.NewOrphanSessionCheck())

internal/doctor/town_git_check.go

@@ -0,0 +1,71 @@
+package doctor
+
+import (
+	"os"
+	"path/filepath"
+)
+
+// TownGitCheck verifies that the town root directory is under version control.
+// Having the town harness in git is optional but recommended for:
+// - Backing up personal Gas Town configuration and operating history
+// - Tracking mail and coordination beads
+// - Easier federation across machines
+type TownGitCheck struct {
+	BaseCheck
+}
+
+// NewTownGitCheck creates a new town git version control check.
+func NewTownGitCheck() *TownGitCheck {
+	return &TownGitCheck{
+		BaseCheck: BaseCheck{
+			CheckName:        "town-git",
+			CheckDescription: "Verify town root is under version control",
+		},
+	}
+}
+
+// Run checks if the town root has a .git directory.
+func (c *TownGitCheck) Run(ctx *CheckContext) *CheckResult {
+	gitDir := filepath.Join(ctx.TownRoot, ".git")
+	info, err := os.Stat(gitDir)
+
+	if os.IsNotExist(err) {
+		return &CheckResult{
+			Name:    c.Name(),
+			Status:  StatusWarning,
+			Message: "Town root is not under version control",
+			Details: []string{
+				"Your town harness contains personal configuration and operating history",
+				"Version control makes it easier to backup and federate across machines",
+			},
+			FixHint: "Run 'git init' in your town root to initialize a repository",
+		}
+	}
+
+	if err != nil {
+		return &CheckResult{
+			Name:    c.Name(),
+			Status:  StatusError,
+			Message: "Failed to check town git status: " + err.Error(),
+		}
+	}
+
+	// Verify it's actually a directory (not a file named .git)
+	if !info.IsDir() {
+		return &CheckResult{
+			Name:    c.Name(),
+			Status:  StatusWarning,
+			Message: "Town root .git is not a directory",
+			Details: []string{
+				"Expected .git to be a directory, but it's a file",
+				"This may indicate a git worktree or submodule configuration",
+			},
+		}
+	}
+
+	return &CheckResult{
+		Name:    c.Name(),
+		Status:  StatusOK,
+		Message: "Town root is under version control",
+	}
+}

internal/doctor/town_git_check_test.go

@@ -0,0 +1,88 @@
+package doctor
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestNewTownGitCheck(t *testing.T) {
+	check := NewTownGitCheck()
+
+	if check.Name() != "town-git" {
+		t.Errorf("expected name 'town-git', got %q", check.Name())
+	}
+
+	if check.Description() == "" {
+		t.Error("expected non-empty description")
+	}
+
+	if check.CanFix() {
+		t.Error("expected CanFix() to return false")
+	}
+}
+
+func TestTownGitCheck_NoGitDir(t *testing.T) {
+	// Create temp directory without .git
+	tmpDir, err := os.MkdirTemp("", "town-git-test-*")
+	if err != nil {
+		t.Fatalf("failed to create temp dir: %v", err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	ctx := &CheckContext{TownRoot: tmpDir}
+	check := NewTownGitCheck()
+	result := check.Run(ctx)
+
+	if result.Status != StatusWarning {
+		t.Errorf("expected StatusWarning, got %v", result.Status)
+	}
+
+	if result.FixHint == "" {
+		t.Error("expected non-empty FixHint")
+	}
+}
+
+func TestTownGitCheck_WithGitDir(t *testing.T) {
+	// Create temp directory with .git
+	tmpDir, err := os.MkdirTemp("", "town-git-test-*")
+	if err != nil {
+		t.Fatalf("failed to create temp dir: %v", err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	gitDir := filepath.Join(tmpDir, ".git")
+	if err := os.Mkdir(gitDir, 0755); err != nil {
+		t.Fatalf("failed to create .git dir: %v", err)
+	}
+
+	ctx := &CheckContext{TownRoot: tmpDir}
+	check := NewTownGitCheck()
+	result := check.Run(ctx)
+
+	if result.Status != StatusOK {
+		t.Errorf("expected StatusOK, got %v", result.Status)
+	}
+}
+
+func TestTownGitCheck_GitIsFile(t *testing.T) {
+	// Create temp directory with .git as a file (worktree case)
+	tmpDir, err := os.MkdirTemp("", "town-git-test-*")
+	if err != nil {
+		t.Fatalf("failed to create temp dir: %v", err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	gitFile := filepath.Join(tmpDir, ".git")
+	if err := os.WriteFile(gitFile, []byte("gitdir: /some/path"), 0644); err != nil {
+		t.Fatalf("failed to create .git file: %v", err)
+	}
+
+	ctx := &CheckContext{TownRoot: tmpDir}
+	check := NewTownGitCheck()
+	result := check.Run(ctx)
+
+	if result.Status != StatusWarning {
+		t.Errorf("expected StatusWarning for .git file, got %v", result.Status)
+	}
+}