client: Persist draft messages optimistically and on draft events

[gpunto]

Goal

Stop draft messages from being lost when a request does not complete, and from reappearing after they have been deleted.

Closes AND-1373

Contributes to #6388

Implementation

Aligns three gaps with the iOS SDK (DraftMessagesRepository, DraftUpdaterMiddleware):

• Create and delete are optimistic. New onCreateDraftMessageRequest / onDeleteDraftMessagesRequest listener hooks, dispatched from doOnStart, so the local write no longer waits for the response and survives a process death mid-request.
• Result handlers no longer roll back. Success stores the server copy, failure leaves the local draft as is. Previously a permanent create error dropped the draft and a permanent delete error kept it forever.
• Draft events reach the database. draft.updated / draft.deleted only touched MutableGlobalState, so a draft deleted on another device left its Room row behind and SyncManager re-pushed it on every reconnect. draft.deleted has an empty message id, so deletion keys on cid (or parentId for threads), which needed a new DAO query.

No public API change: neither DraftMessageListener nor MessageRepository is in the API dump.

Testing

Two emulators against the demo backend:

• Draft deleted on a second device: reappeared after restart on develop, now stays gone.
• Create and delete failing with an injected 403: draft is kept / removed respectively, and survives a restart.

Unit tests cover both precommit paths and the channel and thread cases for draft.deleted.

[github-actions]

PR checklist ✅

All required conditions are satisfied:

• Title length is OK (or ignored by label).
• At least one pr: label exists.
• Sections ### Goal, ### Implementation, and ### Testing are filled, or the PR is bot-authored.
• An issue is linked (Linear ticket or GitHub issue), or the PR is bot-authored.

🎉 Great job! This PR is ready for review.

[github-actions]

SDK Size Comparison 📏

SDK	Before	After	Difference	Status
stream-chat-android-client	5.96 MB	5.96 MB	0.00 MB	🟢
stream-chat-android-ui-components	11.25 MB	11.25 MB	0.00 MB	🟢
stream-chat-android-compose	12.74 MB	12.74 MB	0.00 MB	🟢

[sonarqubecloud]

Quality Gate failed

Failed conditions
71.4% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud