One calendar for people with more mailboxes than they can track - every invite merged, booking pages under your own name.
Google, Microsoft, iCloud and IMAP calendars merge on iCalUID, meeting room codes and attendee overlap. Each merge keeps its evidence, and anything uncertain is flagged for review instead of guessed.
The ladder runs from ten minutes before to ten minutes after, getting louder once the meeting starts. Acknowledging it or joining the Meet call ends it - an RSVP never does.
Booking pages sit in front of the merged calendar. Free/busy never leaves the server, double-booking is blocked by the database, and Google or Microsoft sends the invite.
