fix: persist session banner dismissals and add hide-banner setting

- Stop overwriting AI session titles with the "Planning session" fallback
  during cross-tab broadcasts before initialPlan has hydrated on resume.
- Persist SessionNotificationBanner dismissals to localStorage keyed by
  updatedAt so they survive refresh and auto-re-show on the next event.
- Add Settings → Appearance toggle to hide the banner entirely.
- Drop the inner scrollbar on the planning question list; let the outer
  pane handle all scrolling.

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

.changeset/fix-session-banner-and-planning-scroll.md

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+"@runfusion/fusion": patch
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+
+Fixes and a new appearance setting for the AI session notification banner and planning mode UI:
+
+- Planning mode question list no longer has its own inner scrollbar nested inside the right pane's scrollbar. The inner `.planning-options` `max-height: 40vh` constraint was removed so longer question lists expand naturally and the outer pane handles all scrolling.
+- After a page refresh, the "AI sessions need your input" banner briefly displayed the real session title and then flipped to the literal default "Planning session". `PlanningModeModal` was broadcasting the fallback title via the cross-tab sync channel before `initialPlan` had hydrated on a resumed session, overwriting the API title. The broadcast now omits the title field when no real title is known, so the API title is preserved.
+- Banner dismissals are now persisted to `localStorage` keyed by session `updatedAt`. A dismissed entry stays hidden across refreshes until the session advances (a new question/event arrives), at which point the dismissal is auto-pruned and the banner re-appears.
+- Added a Settings → Appearance toggle to hide the AI session notification banner entirely.