Fix Google Calendar task sync reliability and rendering

[martin-forge]

Summary

This combines the Google Calendar fixes from #1802, #1832, #1843, and #1844 into one PR. I think they are easier to review together because they touch the same sync path and share metadata assumptions.

• Recurring task reschedules now keep one master event and one detached exception event, with EXDATEs for moved and completed instances.
• Hardened moved recurring occurrence handling so stale exception metadata cannot replace the true original series date when an on-pattern scheduled occurrence is moved.
• TaskCard scheduled-date actions now preserve the clicked recurring occurrence context before updating scheduled, preventing duplicate recurring/detached projections when moving one instance from the card UI.
• Task property writes now map underscored TaskInfo keys such as recurrence_anchor, complete_instances, and skipped_instances to their configured frontmatter fields instead of producing undefined keys.
• Checkbox-backed boolean status updates are normalized for completed-date, auto-archive, webhook, and Google Calendar side effects while preserving boolean frontmatter for Obsidian checkbox properties.
• Zero-duration timed Google events get a minimal end time before FullCalendar list rendering, which prevents the multi-day display bug.
• Task deletions and failed sync writes are queued in plugin data and replayed after reconnect or restart; 404/410 deletes are treated as already clean.
• Create/update/status races are serialized or deduped so duplicate events and overwritten completion ticks are avoided.
• External task-file changes now reconcile to Google Calendar through persisted calendar-relevant fingerprints, including first-startup reconciliation for already-linked tasks and later linked-task changes made while Obsidian was closed, without startup bulk creation for existing unlinked tasks.
• External task completions now reconcile with the auto-archive queue: live or offline file edits that move a task into an auto-archiving status are queued using completion/file timestamps, due archives are processed, existing timers are not reset, and archived linked tasks stay queued until Google cleanup succeeds.
• Calendar descriptions are plain text: wikilinks render as labels, and the Obsidian URL is included as text instead of an HTML anchor. This avoids raw HTML in Apple Calendar; whether it is clickable still depends on the calendar client.

Validation

• npm test -- --runInBand tests/unit/issues/issue-google-calendar-delete-retry-queue.test.ts tests/unit/issues/issue-google-calendar-duplicate-investigation.test.ts tests/unit/issues/issue-1696-gcal-recurring-reschedule.test.ts tests/unit/issues/issue-google-calendar-external-file-reconciliation.test.ts tests/unit/issues/issue-google-calendar-archive-reliability.test.ts tests/unit/issues/issue-1695-archived-task-orphaned-calendar-event.test.ts tests/unit/issues/issue-1687-calendar-recreate-date-preservation.test.ts tests/unit/issues/issue-1823-zero-duration-google-calendar-list-duplication.test.ts
• npm test -- --runInBand tests/unit/services/TaskService.test.ts tests/unit/issues/issue-850-auto-archive-checkbox-status.test.ts
• npm test -- --runInBand tests/unit/issues/issue-google-calendar-archive-reliability.test.ts tests/unit/issues/issue-1696-gcal-recurring-reschedule.test.ts
• npm run typecheck
• npm run build
• TZ=UTC npm test -- --runInBand
• git diff --check

Note: a non-UTC local timezone check still reproduces the same two pre-existing timezone-sensitive failures in due-date-timezone-inconsistency.test.ts and issue-327-failing-test.test.ts; the UTC run passes.