Interaction types (likes, bookmarks, reposts) have no body content in
their JF2 properties. The timeline entry was created with empty content,
showing blank posts in Phanpy/Moshidon. Now synthesizes display content
(e.g. "Liked: https://...") matching backfill-timeline.js behavior.
Own Micropub posts weren't appearing in Mastodon Client API timelines
(Phanpy/Moshidon) because there was no mechanism to add them to
ap_timeline. The inbox round-trip doesn't work (we don't follow
ourselves) and startup backfill only runs once.
Now the AP syndicator adds the post to ap_timeline after successful
delivery, using addTimelineItem ($setOnInsert — idempotent). Content
flows directly from Micropub properties with proper HTML links.