feat(calendar): improve parity for recurrence, availability, and selection

[salmonumbrella]

Summary

• Add --cal, --calendars, and --all flags to freebusy and conflicts commands for calendar selection by name/index
• Fix recurring event instance ID handling in edit/delete scope operations (--scope single and --scope future now work when given an instance event ID instead of the master)
• Add day_of_week/dayOfWeek to calendar time JSON and text output
• Add GOG_FORCE_OUTPUT env alias and --non-interactive auto-JSON when stdout is non-TTY
• Fix contacts helper function signatures and remove unused primaryURL
• Extract shared calendar resolution helpers and introduce scopeResult struct (code review follow-up)

Test plan

• All existing tests pass (go test ./... -count=1)
• New tests for resolveRecurringSeriesID (master, instance, non-recurring)
• New tests for dedupeCalendarTargets and collectCalendarInputs
• New tests for --plain overriding GOG_FORCE_OUTPUT and --non-interactive
• New integration tests for freebusy name resolution and conflicts --all
• go vet ./... clean
• go build ./... clean

🤖 Generated with Claude Code

[steipete]

Landed via reviewed rebase onto main.

• Gate: go test ./internal/cmd -run 'Test(ResolveRecurring|ApplyUpdateScopeFuture|CalendarDeleteCmd_ScopeFuture_InstanceEventID|CalendarFreeBusyCmd_ResolvesCalendarName|CalendarConflictsCmd_AllCalendarsSelection)' -count=1, make lint, make test, make ci\n- Land commit: 251a605\n- Merge commit: e19bac1\n\nNarrowed the PR to the current-main fit: kept the recurring instance/series fixes plus freebusy/conflicts selection parity, and dropped the stale contacts/root overlap.\n\nThanks @salmonumbrella!