docs: cut jump-to-date (M2) from V1 scope

The date-picker half of M2 is dropped entirely; the "Today" half already
shipped in v0.5. V1 is now feature-complete and only a polish/QA pass
remains before v1.0.

Updated the living planning docs (ROADMAP, STATE, REQUIREMENTS) and the
design spec; corrected the v0.5.0 CHANGELOG note that promised M2 would
return in v1.0.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.planning/REQUIREMENTS.md

@@ -17,7 +17,7 @@ See full design spec: `docs/superpowers/specs/2026-06-08-calendar-app-design.md`
 - [ ] Day view (S3)
 - [ ] Event Detail Sheet (S4)
 - [ ] Multi-Calendar Filter (M3)
-- [ ] Today button + Jump-to-Date (M2)
+- [x] Today button (M2) — shipped v0.5; Jump-to-Date **cut from scope**
 - [ ] View-Switcher (M1)
 - [ ] Settings screen (M4)
 - [ ] Empty / no-permission / no-calendars states