GET /api/history/{session_id} skips messages whose metadata has `hidden` (e.g.
compaction summaries kept for AI context, not shown to the user) on the
in-memory path. The DB fallback — used when the in-memory history is empty,
e.g. after a restart — built the response from every stored row with no such
filter, so hidden messages leaked to the client on DB-served sessions.
Filter `hidden` out of the response on the DB path too. The rebuilt in-memory
session.history still includes them, so AI context (the compaction summaries)
is preserved.
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
