Mirror "Maybe" (tentative RSVP) events instead of dropping them.
Previously, with "Mirror accepted events only" on, events you'd replied
tentative to were skipped entirely. They're now mirrored with a "Maybe: "
marker in the title (after the normal prefix) and written with tentative
availability so Calendar shows them hatched. The marker is applied for any
tentative RSVP regardless of the accepted-only setting; an accepted<->
tentative flip re-syncs the title. Not carried on the merge path
(mergeGapMin > 0), which already discards per-event titles.
Block gains a `tentative` flag (in ==/hash); accepted-only gate lets
.tentative through alongside .accepted.
All unit tests pass.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>