Release 0.7.0

First public-facing release shaped for MELPA/ELPA submission. Highlights:

- Calendar URL integration: chime-calendar-url + left-click modeline -> browser
- Day-wide / all-day event handling with advance-notice window
- Severity refactor: chime-alert-intervals replaces alert-time + alert-severity
- Async-first event fetching via subprocess
- Public API surface trimmed to four symbols (chime-mode,
  chime-validate-configuration, chime-refresh-modeline,
  chime-done-keywords-predicate) plus chime-debug-*
- Declined org-gcal events filtered out of tooltip, modeline, notifications
- Eask-based test runner, undercover coverage, 90.2% line coverage on chime.el
- 677 tests; integration suite tagged :slow for fast inner-loop iteration