OpenCode 2: deleted-session cleanup depends on one live event loop, which stops on the first error #745

Magic Context: code references at v0.49.15. OpenCode 2 only.

1. No orphan sweep on OpenCode 2

features/magic-context/message-index.ts:1016-1038: on opencode2 the orphan sweep parks itself for a day and returns "unavailable: OpenCode 2 keeps its sessions in session_v2, which this sweep does not read". The only cleanup is the live session.deleted handler (v2/hooks/context.ts:1336-1343) plus retryPendingSessionCleanups, which retries only sessions already marked there.

So any session deleted while this process isn't subscribed keeps its FTS, tags, compartments and embeddings forever: deletes from another OpenCode process or the CLI, deletes while OpenCode is closed, and a boot with storage unavailable (if (db) skips cleanup).

(When we bulk-deleted 811 subagent sessions through the running server, the event path did clean them all; this is about the cases where the event isn't seen.)

Suggestion: an OpenCode 2 sweep that diffs session_v2 ids against the session-scoped tables; V2StoreReader already reads session_v2.

2. One exception ends the event loop for the process lifetime

v2/hooks/context.ts:1300-1385: the try wraps the whole for await; the catch logs "v2 usage subscription failed" and nothing resubscribes. Calls in the session.deleted branch can throw (markSessionCleanupPending / clearSession on SQLITE_BUSY under multi-process contention, nativeFoldReplay.forget, transform.clearSessionLogState). After one throw, deletion cleanup, usage recording and revert handling stop for that process.

Suggestion: try/catch per event, and resubscribe when the stream ends or errors.

3. A subagent can be classified as primary for good

storage-meta-session.ts:112-146 reads the parent link only when the session_meta row is first created. If that lookup returns null (row not yet visible, or the read throws), a primary row is inserted and kept ("retain their served mode"), so historian eligibility, primary guidance and tool hiding stay wrong for that session. Rare, since OpenCode 2 writes parent_id first. Suggestion: retry on null instead of inserting a primary row. Related: #612 (closed).