v0.1.0-alpha.89

fix(ui): rehydrate web/legacy threads on desktop when engine=claude-code

When settings.engine === 'claude-code' (the desktop default), every thread
went through the engine-rehydrate path that requires a claude session_id
mapping. For threads created via the web app or legacy mode there's no
claudeSessionByThread[threadId] entry on this device, so the lookup
returned null and ChatSurface set blocks=[] → empty welcome state.

Fall back to fetching by threadId itself when no engine session mapping
exists. The edge GET /v1/threads/:id/messages is keyed by row id which
works for both schemes.

Bump to alpha.89 to ship the fix; alpha.88 GH Release has the bug and
should be superseded as latest by this tag's CI run.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>