feat(calendar): context-aware sidebar date clicks (Calendar view vs Journal)

[h4yfans]

What

The global right-sidebar mini-calendar now behaves based on the active tab:

Active tab	Sidebar day click
Calendar	Re-anchors the current calendar view (day/week/month/year) in place
Anything else	Opens/focuses Journal at that date (unchanged)

The Today button in the sidebar follows the same branch.

Why

Before this change, every sidebar day click navigated to the Journal tab — disruptive when the user is actively working in Calendar, since it yanked them out of their Month/Week/Year view just to focus a date. Making the sidebar context-aware lets the same UI serve both workflows: fast navigation inside Calendar, and quick journaling from anywhere else.

How

• New CalendarViewContext (apps/desktop/src/renderer/src/contexts/calendar-view-context.tsx) — holds the single anchorDate shared between CalendarPage and GlobalDayPanel. Mirrors the DayPanelContext pattern (null sentinel + throwing hook).
• GlobalDayPanel branches handleDateSelect / handleTodayClick on useActiveTab()?.type === 'calendar'.
• CalendarPage swaps its local useState(getTodayDate) for useCalendarView(). No other handler changes — the React useState setter identity is preserved through context, so setAnchorDate((current) => ...) functional updates in handlePrevious / handleNext keep working.
• All four views handled by one branch: getRangeForView(view, anchorDate) already derives day/week/month/year ranges from a single anchor, so setting anchorDate = clickedDate re-centers whichever view is active. No per-view code.
• Test wrapper updated: tests/utils/render.tsx wraps the new provider inside the existing DayPanelProvider — one edit fixed all 3 calendar test files without per-test churn.

Type

• feat — new feature

Test plan

• Unit tests updated (central renderWithProviders wrapper)
• Manual testing TODO:
  • Notes tab → click sidebar day → Journal opens at date (regression)
  • Journal tab → click sidebar day → Journal re-focuses date (regression)
  • Calendar / Month view → click sidebar day in another month → Month view scrolls, no tab switch
  • Calendar / Week view → click sidebar day → week grid re-centers
  • Calendar / Year view → click sidebar day in another year → year grid changes
  • Calendar / Day view → click sidebar day → Day view and sidebar stay in sync
  • Today button from Calendar tab → anchor jumps to today, no tab switch
• Verification run in this branch: pnpm --filter desktop typecheck:web clean, pnpm lint 0 errors, pnpm test — 6912 passed, 0 failed.

Checklist

• Self-reviewed the diff
• No hardcoded secrets or credentials
• Files stay under ~500 LOC
• Follows immutable data patterns