- move project draft thread ID persistence/actions into `composerDraftStore`
- remove legacy `projectDraftThreads` module and update `ChatView`/`Sidebar` callers
- keep image dedupe stable across hydration and avoid revoking blob URLs on composer clear
- add store tests for project-thread mapping and composer clear behavior
- drop deprecated model slug aliases (`gpt-5`, `gpt-5-codex`, `gpt-5-codex-spark`)