Planning sidebar's `/api/ai-sessions` listing filtered out `complete`
rows, so a session that finished while the modal was closed disappeared
on refresh even though the result was still in SQLite. Add
`?includeCompleted` / `?includeArchived` flags and a new `archived`
column (migration 57) so users can hide terminal sessions on demand
without deleting them; only `complete`/`error` rows are archivable so
live agents can't be orphaned.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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