Fix recurring exception sync for rescheduled recurring tasks

[martin-forge]

Maintainer note

Ready to merge. This is distinct from #1843: it fixes recurring task exception state and detached exception events. The only overlap is calendar cleanup. If #1843 lands first, this PR should be rebased so detached exception cleanup uses #1843's retry-safe deletion queue. If this lands first, #1843 should be rebased so its persisted event index/recovery also tracks detached exception event IDs.

Summary

• Preserve the original RRULE occurrence date when a scheduled-anchor recurring task is moved off-pattern.
• Sync moved occurrences to Google Calendar as a recurring master with an EXDATE plus one detached exception event.
• Clean up detached exception metadata/events when the moved occurrence is completed, skipped, archived, deleted, or unlinked.
• Keep local calendar recurring rendering aligned by hiding original pattern dates represented by moved-occurrence metadata.

Closes #1696.

Validation

• TZ=UTC npm test -- --runInBand
• npm run docs:check
• npm run i18n:sync
• npm run lint
• npm run typecheck
• npm run build:test
• obsidian plugin:reload id=tasknotes vault=test

[martin-forge]

Cross-PR compatibility note from auditing against #1843:

This PR remains a distinct fix: #1843 does not add the recurring-exception metadata, moved-original-date tracking, local calendar rendering changes, or detached Google exception event flow introduced here.

The only substantive overlap is cleanup. If #1843 lands before this PR, please route this PR's primary + detached exception event cleanup through #1843's retry-safe deletion queue and keep 404/410 deletes as success. If this PR lands first, #1843 should be rebased so its persisted event index and startup recovery track both googleCalendarEventId and googleCalendarExceptionEventId; otherwise a task file deleted while Obsidian is closed could still leave a detached recurring exception event orphaned.

[martin-forge]

Superseded by #1851, which consolidates the Google Calendar fixes into one ready-to-review PR.