Use plain text Google Calendar descriptions

[martin-forge]

Maintainer note

Ready to merge independently. This PR only changes Google Calendar task description formatting. If #1843 lands first, the expected follow-up is a small rebase around TaskCalendarSyncService/description tests, preserving the plain-text output and visible Obsidian URI.

Summary

• render Google Calendar task descriptions as plain text instead of HTML anchors
• strip Obsidian wiki/markdown link syntax from project and context labels
• keep the Obsidian URI visible so clients that do not support custom-scheme anchors do not show broken HTML

Testing

• npm test -- tests/services/TaskCalendarSyncService.test.ts --runInBand
• npm run typecheck
• npm run build:test
• npm run lint -- --quiet
• obsidian plugin:reload id=tasknotes vault=test

[martin-forge]

Cross-PR audit note: I checked this against the other open Google Calendar PRs. This description-formatting PR is behaviourally independent of #1802, #1832, and #1843. If #1843 merges first, the only expected work here is a small rebase around TaskCalendarSyncService/description tests; preserve this PR's plain-text description output and visible Obsidian URI.

[martin-forge]

Superseded by #1851, which consolidates the Google Calendar fixes into one ready-to-review PR.