src/lobby.security.test.ts proves non-drivers are refused, chat HTML stays text, floods collapse, and a mute survives a reconnect · arm

The local half of the Sentinel pass from pull #25, landed on its own.

Done:

[ ] A signed-in person who is not driving gets 403 on /torque, /move, /pose/go, /play and /record; /stop is the owner's alone.
[ ] Chat text containing HTML and <script> is stored and relayed as plain text; non-JSON and non-object frames get an error reply.
[ ] 300 chat frames and 300 join frames from one person give one chat line and one queue place.
[ ] Only the owner can mute or end a turn, and a mute survives a reconnect.
[ ] Test-only: no change outside Software/so101/src/lobby.security.test.ts; bun --cwd Software/so101 test passes.

The file exists on branch smith/20-public-launch-check-a-stranger-watches-s (pull #25), minus the frame-cap test, which belongs to its own issue.

src/lobby.security.test.ts proves non-drivers are refused, chat HTML stays text, floods collapse, and a mute survives a reconnect #124