fix(storage): add reconnectMu RLock protection to prevent race condition (#1054)

Add missing reconnectMu.RLock() protection to storage methods that were
vulnerable to the same race condition fixed in GH#607. The FreshnessChecker
can trigger reconnect() which closes s.db while queries are in flight,
causing "database is closed" errors during daemon export operations.

Protected methods:
- labels.go: GetLabelsForIssues (GetLabels intentionally unprotected - called from GetIssue which holds lock)
- comments.go: GetIssueComments, GetCommentsForIssues
- dependencies.go: GetDependencyCounts, GetDependencyRecords, GetAllDependencyRecords, GetDependencyTree, loadDependencyGraph
- config.go: SetConfig, GetConfig, GetAllConfig, DeleteConfig, SetMetadata, GetMetadata
- dirty.go: MarkIssueDirty, GetDirtyIssues, GetDirtyIssueHash, GetDirtyIssueCount
- events.go: GetEvents, GetStatistics, GetMoleculeProgress
- hash.go: All hash methods
- hash_ids.go: GetNextChildID, ensureChildCounterUpdated (getNextChildNumber unprotected - called internally)

Internal helpers called from already-locked contexts intentionally omit
RLock to avoid deadlock (Go's RWMutex doesn't support recursive locking).

Fixes: bd-vx7fp

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

Executed-By: beads/crew/dave
Rig: beads
Role: crew

internal/storage/sqlite/hash_ids.go

@@ -11,6 +11,7 @@ import (
 
 // getNextChildNumber atomically increments and returns the next child counter for a parent issue.
 // Uses INSERT...ON CONFLICT to ensure atomicity without explicit locking.
+// Note: Caller must hold reconnectMu.RLock() - this is an internal method.
 func (s *SQLiteStorage) getNextChildNumber(ctx context.Context, parentID string) (int, error) {
 	var nextChild int
 	err := s.db.QueryRowContext(ctx, `
@@ -30,6 +31,11 @@ func (s *SQLiteStorage) getNextChildNumber(ctx context.Context, parentID string)
 // Returns formatted ID as parentID.{counter} (e.g., bd-a3f8e9.1 or bd-a3f8e9.1.5)
 // Works at any depth (max 3 levels)
 func (s *SQLiteStorage) GetNextChildID(ctx context.Context, parentID string) (string, error) {
+	// Hold read lock during database operations to prevent reconnect() from
+	// closing the connection mid-query (GH#607 race condition fix)
+	s.reconnectMu.RLock()
+	defer s.reconnectMu.RUnlock()
+
 	// Validate parent exists
 	var count int
 	err := s.db.QueryRowContext(ctx, `SELECT COUNT(*) FROM issues WHERE id = ?`, parentID).Scan(&count)
@@ -72,6 +78,11 @@ func (s *SQLiteStorage) GetNextChildID(ctx context.Context, parentID string) (st
 // with explicit IDs (via --id flag or import) rather than GetNextChildID.
 // (GH#728 fix)
 func (s *SQLiteStorage) ensureChildCounterUpdated(ctx context.Context, parentID string, childNum int) error {
+	// Hold read lock during database operations to prevent reconnect() from
+	// closing the connection mid-query (GH#607 race condition fix)
+	s.reconnectMu.RLock()
+	defer s.reconnectMu.RUnlock()
+
 	_, err := s.db.ExecContext(ctx, `
 		INSERT INTO child_counters (parent_id, last_child)
 		VALUES (?, ?)