Fix FOREIGN KEY constraint failed when operating on non-existent issues

Fixes #325

- Fix CloseIssue to check rows affected before inserting event
- Fix RemoveLabel to check rows affected before inserting event
- Fix UpdateIssueID to check rows affected before inserting event
- Prevent orphan events and confusing error messages

Amp-Thread-ID: https://ampcode.com/threads/T-aa765a68-5cc4-465b-a2f6-aa008933c11e
Co-authored-by: Amp <amp@ampcode.com>

internal/storage/sqlite/labels.go

@@ -20,11 +20,20 @@ func (s *SQLiteStorage) executeLabelOperation(
 	operationError string,
 ) error {
 	return s.withTx(ctx, func(tx *sql.Tx) error {
-		_, err := tx.ExecContext(ctx, labelSQL, labelSQLArgs...)
+		result, err := tx.ExecContext(ctx, labelSQL, labelSQLArgs...)
 		if err != nil {
 			return fmt.Errorf("%s: %w", operationError, err)
 		}
 
+		rows, err := result.RowsAffected()
+		if err != nil {
+			return fmt.Errorf("failed to check rows affected: %w", err)
+		}
+		if rows == 0 {
+			// No change made (label already existed or didn't exist), so don't record event
+			return nil
+		}
+
 		_, err = tx.ExecContext(ctx, `
 			INSERT INTO events (issue_id, event_type, actor, comment)
 			VALUES (?, ?, ?, ?)

internal/storage/sqlite/sqlite.go

@@ -711,7 +711,7 @@ func (s *SQLiteStorage) UpdateIssueID(ctx context.Context, oldID, newID string,
 	}
 	defer func() { _ = tx.Rollback() }()
 
-	_, err = tx.ExecContext(ctx, `
+	result, err := tx.ExecContext(ctx, `
 		UPDATE issues
 		SET id = ?, title = ?, description = ?, design = ?, acceptance_criteria = ?, notes = ?, updated_at = ?
 		WHERE id = ?
@@ -720,6 +720,14 @@ func (s *SQLiteStorage) UpdateIssueID(ctx context.Context, oldID, newID string,
 		return fmt.Errorf("failed to update issue ID: %w", err)
 	}
 
+	rows, err := result.RowsAffected()
+	if err != nil {
+		return fmt.Errorf("failed to get rows affected: %w", err)
+	}
+	if rows == 0 {
+		return fmt.Errorf("issue not found: %s", oldID)
+	}
+
 	_, err = tx.ExecContext(ctx, `UPDATE dependencies SET issue_id = ? WHERE issue_id = ?`, newID, oldID)
 	if err != nil {
 		return fmt.Errorf("failed to update issue_id in dependencies: %w", err)
@@ -812,7 +820,7 @@ func (s *SQLiteStorage) CloseIssue(ctx context.Context, id string, reason string
 	}
 	defer func() { _ = tx.Rollback() }()
 
-	_, err = tx.ExecContext(ctx, `
+	result, err := tx.ExecContext(ctx, `
 		UPDATE issues SET status = ?, closed_at = ?, updated_at = ?
 		WHERE id = ?
 	`, types.StatusClosed, now, now, id)
@@ -820,6 +828,14 @@ func (s *SQLiteStorage) CloseIssue(ctx context.Context, id string, reason string
 		return fmt.Errorf("failed to close issue: %w", err)
 	}
 	
+	rows, err := result.RowsAffected()
+	if err != nil {
+		return fmt.Errorf("failed to get rows affected: %w", err)
+	}
+	if rows == 0 {
+		return fmt.Errorf("issue not found: %s", id)
+	}
+
 	_, err = tx.ExecContext(ctx, `
 		INSERT INTO events (issue_id, event_type, actor, comment)
 		VALUES (?, ?, ?, ?)