fix reconciliation, activity feed, and connection serialization
- use patch_rows instead of upsert_rows when marking observations superseded (fixes empty vector error)
- show replies in homepage activity feed (posts_and_author_threads)
- remove erroneous .upper() on connectionType (lexicon values are lowercase)
- fix test assertions to match actual record shape
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>