feat(x): visual calendar with write support, multi-calendar, and assistant tools

[hrsvrn]

Summary

I replaced the flat Meetings list with a full visual calendar and took it from read-only to a complete scheduling surface: writes (create/edit/delete/RSVP), drag-to-reschedule, recurring-event handling, availability sharing, secondary Google calendars, a tray next-meeting countdown, and assistant calendar tools.

Visual calendar (2d66e5f)

• New Calendar tab with month grid, week time-grid, and agenda mode, with directional slide transitions between views and periods.
• Meetings view is folded into the calendar as agenda mode — the Meetings tab, sidebar entry, and view state are removed, and all old entry points (deep links, open-view, home, tour, credit rewards) land on calendar agenda.
• Extracted shared calendar-event parsing/formatting into lib/calendar-events.ts + a use-calendar-events hook + a shared event details popover (behavior unchanged).
• Widened calendar sync from -7/+14 days to ±60 and added pagination to events.list (it was silently capped at 250 events).

Calendar write (03eb64f)

• Five new calendar:* IPC channels (getWriteStatus / createEvent / updateEvent / deleteEvent / respond) backed by core/knowledge/calendar_write.ts.
• Drag/click quick-create in month and week grids; inline title/date/time editing, delete, and RSVP in the event details popover; meeting-note matching for event links.
• Successful writes persist the returned event into calendar_sync/ for an instant UI refresh, then wake the sync loop to reconcile.
• Write UI is gated by useCalendarWriteAccess, which re-checks after OAuth connects.

Upgrades (fc94ceb)

• Keyboard shortcuts: T/J/K/arrows for navigation, D/W/M/A for views, C to create, S for availability.
• Drag-to-reschedule and bottom-edge resize with optimistic updates.
• Recurring-event awareness: series badge, this-event vs whole-series delete.
• Availability sharing: drag free windows, copy formatted text with timezone.
• Multi-calendar: secondary Google calendars sync (calendars.json, per-calendar colors, visibility toggles, calendarId-routed writes).
• Tray next-meeting countdown with one-click "Join & take notes".
• Assistant calendar tools (list / find-free-slots / create / update / delete / RSVP) behind a new calendar skill.

⚠️ Shipping dependency

OAuth scopes are upgraded from calendar.events.readonly to calendar.events, plus calendarlist.readonly for multi-calendar. The hosted rowboat-mode OAuth backend must add both scopes in lockstep before this ships. The sync loop accepts either grant, so legacy readonly connections keep syncing until the startup scope migration prompts a reconnect.

Test plan

• date-grid unit tests added; tools catalog test updated
• npm run deps, lint, typecheck pass
• E2E pass over write flows (create/edit/delete/RSVP) against a real Google account

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