feat: consolidate maintenance commands into bd doctor --fix (bd-bqcc)

Add new Maintenance category to bd doctor with checks for:
- Stale closed issues (older than 30 days)
- Expired tombstones (older than TTL)
- Compaction candidates (info only)

Add fix handlers for cleanup and tombstone pruning via bd doctor --fix.
Add deprecation hints to cleanup, compact, and detect-pollution commands
suggesting users try bd doctor instead.

This consolidation reduces cognitive load - users just need to remember
'bd doctor' for health checks and 'bd doctor --fix' for maintenance.

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

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

cmd/bd/cleanup.go

@@ -20,7 +20,11 @@ type CleanupEmptyResponse struct {
 
 // Hard delete mode: bypass tombstone TTL safety, use --older-than days directly
 
-// TODO: Consider consolidating into 'bd doctor --fix' for simpler maintenance UX
+// showCleanupDeprecationHint shows a hint about bd doctor --fix (bd-bqcc)
+func showCleanupDeprecationHint() {
+	fmt.Fprintln(os.Stderr, ui.RenderMuted("💡 Tip: 'bd doctor --fix' can now cleanup stale issues and prune tombstones"))
+}
+
 var cleanupCmd = &cobra.Command{
 	Use:     "cleanup",
 	GroupID: "maint",
@@ -252,6 +256,11 @@ SEE ALSO:
 				}
 			}
 		}
+
+		// bd-bqcc: Show hint about doctor --fix consolidation
+		if !jsonOutput {
+			showCleanupDeprecationHint()
+		}
 	},
 }