fix: bd sync works when on sync branch (GH#519)

When sync.branch is set to the current branch (e.g., main), bd sync
now commits directly instead of failing with a worktree error.

Changes:
- sync.go: Detect when current branch == sync branch and skip worktree
- sync.go: Show appropriate messages for direct-mode commits/pulls
- doctor.go: Change from Error to OK status when on sync branch

The fix allows users to work directly on the sync branch without
having to switch to a different branch for bd sync to work.

Closes: GH#519

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

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

cmd/bd/doctor.go

@@ -2498,16 +2498,14 @@ func checkSyncBranchConfig(path string) doctorCheck {
 		currentBranch = strings.TrimSpace(string(output))
 	}
 
-	// CRITICAL: Check if we're on the sync branch - this is a misconfiguration
-	// that will cause bd sync to fail trying to create a worktree for a branch
-	// that's already checked out
+	// GH#519: Check if we're on the sync branch - this is supported but worth noting
+	// bd sync will commit directly instead of using worktree when on sync branch
 	if syncBranch != "" && currentBranch == syncBranch {
 		return doctorCheck{
 			Name:    "Sync Branch Config",
-			Status:  statusError,
-			Message: fmt.Sprintf("On sync branch '%s'", syncBranch),
-			Detail:  fmt.Sprintf("Currently on branch '%s' which is configured as the sync branch. bd sync cannot create a worktree for a branch that's already checked out.", syncBranch),
-			Fix:     "Switch to your main working branch: git checkout main",
+			Status:  statusOK,
+			Message: fmt.Sprintf("On sync branch '%s' (direct mode)", syncBranch),
+			Detail:  fmt.Sprintf("Currently on sync branch '%s'. bd sync will commit directly instead of using worktree.", syncBranch),
 		}
 	}