The AI assistant's "more actions" need host calls today's plugin API
lacks. Area c of lib/plugin-sandbox/assistant adds them:
- `calendar.respond(emailId, status)`, new permission calendar:respond:
answers an invitation of the user's own account through
lib/calendar-rsvp.ts, like the reader's banner
- `calendar.deleteEvent` now returns an undo token for a single event;
`calendar.undoDelete` creates it again from the host's copy
- `filters.list/create/undo` over Settings > Filters' model; forward,
redirect, reject, discard and keep are refused, and so are folders
that are shared or not the account's own
- `email.batch/undoBatch`: up to 200 messages through the store's
batch functions, restore points first, one entry in the undo history
- `vacation.get` also says whether the out-of-office forwards mail
- `app.describeSettings`, `app.setSettings` and `app.undoSettings`, new
permission settings:change, over the allow-list in
lib/settings-schema.ts, refusing locked, hidden, restricted and gated
settings when the change is made
Undo tokens stay in the host for 30 minutes, bound to the plugin and
the account. app.getSettings now shows every setting setSettings may
change. settings:write's text is reworded to what it gates (tags).
plugin-host-api-app-info gains a test; its other assertions are as
they were.
