Keep local interactions responsive

[ComputelessComputer]

Cancel dismissible sharing work, keep calendar network activity out of the local write queue, and scope persistence flushes.

Supersedes #6204, which GitHub automatically closed when its stacked base #6202 merged and was deleted.

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Note

Medium Risk
Touches calendar disconnect invalidation, global write-queue flush semantics, and sharing lifecycle—areas where races could affect data consistency, though behavior is heavily test-covered.

Overview
Improves local responsiveness by narrowing when the app waits on SQLite writes, moving slow calendar work off the write queue, and making session sharing dismissible without stray side effects.

Database write queue — Keyed flushDatabaseWrites now loops until targeted keys are idle (including writes enqueued mid-flush) and still surfaces the first failure after draining. Adds flushDatabaseWritesByPrefix and flushDatabaseWritesWithin (timeout without abandoning in-flight writes). Call sites flush only relevant keys (e.g. session:{id}, attachment-transfers, shared-note-cache:{viewer}) instead of the whole queue. Exit/relaunch use a 5s bounded flush with Promise.allSettled so settings save can finish even if the DB flush times out.

Calendar sync — Full sync runs on a separate enqueueCalendarSync chain; only inventory/event commits use enqueueDatabaseWrite("calendar-sync", …). Generation and a disconnected-connection set invalidate in-flight work so disconnect/reconnect cannot restore stale data; tombstone failures roll back the disconnect marker. Deeplink handler triggers syncCalendarEvents after disconnect and allowReconnectedCalendarConnections on reconnect.

Session sharing — Share popover can close anytime; preparation uses attempt IDs and abort controllers so dismissed work does not publish or show errors. ShareOperationAbortedError suppresses toasts on cancel; invitation rollback respects abort. General access scope UI is restrict-only (link/workspace scope flows removed). Sync state loads after scoped flushes including sessionId.

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