feat(doctor): add database corruption recovery to --fix

Adds automatic database recovery when bd doctor --fix detects corruption:
- Detects SQLite corruption (malformed database, SQLITE_CORRUPT errors)
- Backs up corrupted database before recovery attempt
- Rebuilds from JSONL if available (issues.jsonl, deletions.jsonl)
- Falls back to fresh database if JSONL unavailable
- Reports recovery results (issues imported, success/failure)

Recovery is triggered automatically by --fix when corruption is detected.
No manual intervention required.

cmd/bd/doctor.go

@@ -375,6 +375,9 @@ func applyFixList(path string, fixes []doctorCheck) {
 			err = fix.DatabaseVersion(path)
 		case "Schema Compatibility":
 			err = fix.SchemaCompatibility(path)
+		case "Database Integrity":
+			// Corruption detected - try recovery from JSONL
+			err = fix.DatabaseCorruptionRecovery(path)
 		case "Repo Fingerprint":
 			err = fix.RepoFingerprint(path)
 		case "Git Merge Driver":
@@ -432,6 +435,10 @@ func applyFixList(path string, fixes []doctorCheck) {
 			// No auto-fix: compaction requires agent review
 			fmt.Printf("  ⚠ Run 'bd compact --analyze' to review candidates\n")
 			continue
+		case "Large Database":
+			// No auto-fix: pruning deletes data, must be user-controlled
+			fmt.Printf("  ⚠ Run 'bd cleanup --older-than 90' to prune old closed issues\n")
+			continue
 		default:
 			fmt.Printf("  ⚠ No automatic fix available for %s\n", check.Name)
 			fmt.Printf("  Manual fix: %s\n", check.Fix)
@@ -837,6 +844,12 @@ func runDiagnostics(path string) doctorResult {
 	result.Checks = append(result.Checks, compactionCheck)
 	// Info only, not a warning - compaction requires human review
 
+	// Check 29: Database size (pruning suggestion)
+	// Note: This check has no auto-fix - pruning is destructive and user-controlled
+	sizeCheck := convertDoctorCheck(doctor.CheckDatabaseSize(path))
+	result.Checks = append(result.Checks, sizeCheck)
+	// Don't fail overall check for size warning, just inform
+
 	return result
 }