[epic] Teardown is a hand-maintained roll-call, not a registry

[ctoth]

Root cause: teardown is a hand-maintained roll-call, not a registry

MudClient.cleanupConnection (src/client.ts:261-282) resets ~13 stores and services by hand, one line each. Any stateful feature that forgets to add itself keeps state across a disconnect it should not, and any teardown that forgets to stop something leaks it.

Instances already filed

• close() leaves local mode armed; sends are silently swallowed #60 close() leaves localMode/localStream armed
• MediaService.shutdown() does not stop playing sounds #67 MediaService.shutdown() never stops playing sounds

Other observed gaps (not yet separately filed)

• Server-pushed Client.Keystrokes bindings are not cleared on disconnect (only on full shutdown), so a prior session's bindings survive into the next connection.

Suggested direction

A resetOnDisconnect registry that stores/services opt into, iterated on cleanup, so adding a feature can't silently omit its own reset.