Test remaining recovery functionality

[ctm]

Do these tests from doc/recovery-1946-test-coverage.md

• Real panic recovery, end to end
  • Build with --features panic-injection
  • set MB2_PANIC_INJECT=act, seat a live event, and confirm:
    • the thread unwinds
    • hand_aborts gains a row
    • clients see the HandAborted reset
    • the event resumes within budget
    • and after enough repeats the terminal fires
      • ring cashed out
      • tournament frozen
      • EventStatusChanged(Suspended) broadcast)
• Unclean-restart boot recovery
  • kill -9 the server mid-hand
  • restart and confirm
    • each suspension_kind IS NULL
    • started event is aborted then recovered/terminated
• Graceful drain -> exit -> boot resume
  • Run the runbook's websocket_tool --schedule-shutdown confirm
    • every event finishes its current hand and suspends,
    • the process exits 0
    • the next boot resumes each event losslessly with its waitlist
• Past-due scheduled start
  • Schedule an event, keep the server down past its start_at, boot, and confirm it starts late.
• Client rendering
  • The HandAborted reset and the ServerGoingDown/ServerShutdownCancelled countdown banners are WASM render paths; check them in a browser
• Player motion restart test
  • Tables combine
    • Fire up a 6-seated event with 7 players
    • have a player lose or quit and have the two tables merge
    • restart the server and make sure it works
  • Player moved from one table to another
    • Fire up a 6-seated event with 9 players
    • have two players lose or quit on the 4 player table to force one player from the 5 player to move to the now 2 player
    • restart the server and make sure the moved player shows up on the right table and can play

Don't forget the rebalance restart test (which isn't in that document).

[ctm]

This is still important, but it's clearly not high priority, or I would have done it by now.

[ctm]

We've already had one tournament accidentally interrupted and restarted successfully. I've also done some work to detect and report non-resumable tournaments (#2053).

Eventually I think I should finish it via a combination of me doing some of the tests, having Claude do some via driving the app itself and verify-in-play. However, currently, having Claude drive or create verify-in-play scenarios is expensive both in wall clock time as well as AI usage. So, I'm going to put this aside for a while.