fix(sqlite): update child_counters when explicit child IDs are created (GH#728)

When creating issues with explicit hierarchical IDs (e.g., bd-test.1, bd-test.2
via --id flag or import), the child_counters table was not being updated.
This caused GetNextChildID to return colliding IDs when later called with
--parent.

Changes:
- Add ensureChildCounterUpdatedWithConn() to update counter on explicit child creation
- Add ParseHierarchicalID() to extract parent and child number from IDs
- Update CreateIssue to call counter update after hierarchical ID validation
- Update EnsureIDs to call counter update when parent exists
- Add post-insert phase in batch operations to update counters after FK
  constraint can be satisfied
- Update tests to reflect new behavior where counter is properly initialized

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

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

internal/storage/sqlite/batch_ops.go

@@ -102,6 +102,30 @@ func bulkMarkDirty(ctx context.Context, conn *sql.Conn, issues []*types.Issue) e
 	return markDirtyBatch(ctx, conn, issues)
 }
 
+// updateChildCountersForHierarchicalIDs updates child_counters for all hierarchical IDs in the batch.
+// This is called AFTER issues are inserted so that parents exist for the foreign key constraint.
+// (GH#728 fix)
+func updateChildCountersForHierarchicalIDs(ctx context.Context, conn *sql.Conn, issues []*types.Issue) error {
+	for _, issue := range issues {
+		if issue.ID == "" {
+			continue // Skip issues that were filtered out (e.g., OrphanSkip)
+		}
+		if parentID, childNum, ok := ParseHierarchicalID(issue.ID); ok {
+			// Only update if parent exists (it should after insert, but check to be safe)
+			var parentCount int
+			if err := conn.QueryRowContext(ctx, `SELECT COUNT(*) FROM issues WHERE id = ?`, parentID).Scan(&parentCount); err != nil {
+				return fmt.Errorf("failed to check parent existence for %s: %w", parentID, err)
+			}
+			if parentCount > 0 {
+				if err := ensureChildCounterUpdatedWithConn(ctx, conn, parentID, childNum); err != nil {
+					return err
+				}
+			}
+		}
+	}
+	return nil
+}
+
 // checkForExistingIDs verifies that:
 // 1. There are no duplicate IDs within the batch itself
 // 2. None of the issue IDs already exist in the database
@@ -271,6 +295,12 @@ func (s *SQLiteStorage) CreateIssuesWithFullOptions(ctx context.Context, issues
 		return wrapDBError("bulk insert issues", err)
 	}
 
+	// Phase 4.5: Update child counters for hierarchical IDs (GH#728 fix)
+	// This must happen AFTER insert so parents exist for the foreign key constraint
+	if err := updateChildCountersForHierarchicalIDs(ctx, conn, issues); err != nil {
+		return wrapDBError("update child counters", err)
+	}
+
 	// Phase 5: Record creation events
 	if err := bulkRecordEvents(ctx, conn, issues, actor); err != nil {
 		return wrapDBError("record creation events", err)