## Why
`thread/attachment/list` lists attachments for a known thread. Clients also need to find the threads associated with a given attachment identity.
## What changed
Add `thread/attachmentOwner/list` to return owning thread IDs and archive status for an exact `attachmentType` and `identityKey`. Support cursor pagination and an optional `archived` filter, including both archived and non-archived threads by default.
Wire the request through the thread store and update documentation, protocol schemas, and generated TypeScript and Python types. The lookup is limited to the configured thread store and reports current membership, not an atomic resource-cleanup check.
## Testing
Extend app-server integration tests to cover exact type-and-key matching, multiple owners, archive filtering, and invalid cursor rejection.
GitOrigin-RevId: 30f4a20e00243d0023246d465a9b95213b3adeb6
## Why
Attachment mutations must coordinate with thread deletion so queued requests cannot use metadata belonging to a deleted thread.
## What changed
- Add typed `ThreadStore` operations for idempotent attachment creation, paginated listing, and removal, with capability detection and unsupported defaults.
- Implement attachment operations for SQLite-backed `LocalThreadStore`, including unloaded threads, and preserve invalid-request and missing-thread errors.
- Coordinate attachment mutations with lifecycle locks and move SQLite cleanup into thread-store deletion. Remove state rows only after rollout deletion, preserving retries after cleanup failures.
- Give the in-memory store ownership of its associated SQLite cleanup and remove duplicate cleanup from the app-server.
## Testing
Add coverage for attachment pagination and idempotency, unsupported stores, error categories, lifecycle exclusion, mutations queued behind single and batch deletion, cleanup failure retries, and in-memory state cleanup. Extend the app-server descendant deletion test to verify SQLite rows are removed.
GitOrigin-RevId: f0157538c7c5c2ee1362ce40eac157101c5d4505
joeytrasatti-openai