feat(calendar): list appointment schedules

[alexuser]

Summary

• Adds gog calendar appointment-schedules list as a read-only slice of appointment schedule support.
• Reuses the existing calendar events listing flow and filters Calendar API Events.list calls with eventTypes=appointmentSchedule.
• Covers the new appointment schedules list behavior with focused JSON/query-param and command-shape tests.

Fixes #329.

Validation

• go test ./internal/cmd -run 'Appointment|ListCalendarEvents'
• go test ./...
• git diff --check

[steipete]

Thanks for the focused PR. I am going to close this one because the current Google Calendar API still does not expose appointment schedules through Events.list.

We verified the underlying request in #329 with the clawdbot test account: passing the appointment schedule event type returns a 400 invalidParameter response, and the allowed eventTypes are birthday, default, focusTime, fromGmail, outOfOffice, and workingLocation. The CLI therefore keeps gog calendar appointments as an explicit diagnostic instead of adding a list command that would fail against the live API.

If Google starts accepting appointment schedules in Events.list, this would be worth revisiting from a fresh branch. For now this is an upstream API limitation rather than a local implementation gap.