fix: media usage check fails closed on database errors; refused deletes checked for partial state

MediaUsageFinder treats a failed query (null result or last_error) as a possible
usage and an incomplete scan, so media-delete refuses without force. A refused
wp_delete_attachment() is write_failed only when the attachment is intact,
otherwise partial_write. media-update: re-read hint on write_failed, normalized
ids in failures, documented lock resolution and kses on restore.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01At3V6SjwbMe6eMzVGW3Hs7

src/Integrations/Media/MediaMetaWriter.php

@@ -12,6 +12,10 @@ use WP_Post;
  * Writes the editable metadata of an attachment (alt text, title, caption, description) and
  * restores it from a snapshot taken before (lit/media-update rolls a batch back with it).
  * Every failure is a RuntimeException with an internal message for the PHP error log.
+ *
+ * Both apply() and restore() save through wp_update_post(), which runs the kses filters again
+ * for users without unfiltered_html: a caption or description with markup the current user may
+ * not save comes back filtered on restore (like any save of that user in the media library).
  */
 final class MediaMetaWriter
 {