test(sync): add unit tests for gitHasUncommittedBeadsChanges (bd-p7i2)

Extract parseGitStatusForBeadsChanges helper function from
gitHasUncommittedBeadsChanges to enable unit testing without git setup.

Add 14 test cases covering:
- Empty/no changes
- Modified files (staged, unstaged, both)
- Added files (staged, with modifications)
- Untracked files (should return false)
- Deleted files (should return false)
- Renamed/copied files
- Edge cases (short status line)

Part of GH#885 follow-up.

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

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

cmd/bd/sync_git.go

@@ -466,12 +466,18 @@ func gitHasUncommittedBeadsChanges(ctx context.Context) (bool, error) {
 		return false, fmt.Errorf("git status failed: %w", err)
 	}
 
-	// Parse status output - look for modified/added files
-	// Format: XY filename where X=staged, Y=unstaged
-	// M = modified, A = added, ? = untracked
-	statusLine := strings.TrimSpace(string(output))
+	return parseGitStatusForBeadsChanges(string(output)), nil
+}
+
+// parseGitStatusForBeadsChanges parses git status --porcelain output and returns
+// true if the status indicates uncommitted changes (modified or added).
+// Format: XY filename where X=staged, Y=unstaged
+// M = modified, A = added, ? = untracked, D = deleted
+// Only M and A in either position indicate changes we care about.
+func parseGitStatusForBeadsChanges(statusOutput string) bool {
+	statusLine := strings.TrimSpace(statusOutput)
 	if statusLine == "" {
-		return false, nil // No changes
+		return false // No changes
 	}
 
 	// Any status (M, A, MM, AM, etc.) indicates uncommitted changes
@@ -479,11 +485,11 @@ func gitHasUncommittedBeadsChanges(ctx context.Context) (bool, error) {
 		x, y := statusLine[0], statusLine[1]
 		// Check for modifications (staged or unstaged)
 		if x == 'M' || x == 'A' || y == 'M' || y == 'A' {
-			return true, nil
+			return true
 		}
 	}
 
-	return false, nil
+	return false
 }
 
 // getDefaultBranch returns the default branch name (main or master) for origin remote