fix(session): bind a question card's cancel to its prompt

[RonenMars]

Summary

Cancel on a live question card wrote a blind Escape, so tapping it on a card whose gate had already closed interrupted the agent's current turn.
On a streamer with raw keys, a card carrying a registry promptId now sends its Escape through /raw-key bound to that prompt.
The card comes down on the server's reply instead of on the tap.
raw_key_stale takes the card down as a calm notice with nothing written, and any other refusal keeps the card up with a translated error.
Interrupting the agent and the raw keyboard's Escape are a different intent and are unchanged.

Server dependency

The binding takes effect once the streamer honours promptId on escape, tracked in RonenMars/threadbase-streamer#848.
Until then a streamer writes the escape blind and answers 200, exactly as it does today, so this is safe to merge before that lands.

Not covered

Legacy permission and question frames and PTY-scraped cards carry no promptId, so their Cancel keeps the blind Escape.
#841 stays open for the PTY-scraped cards.

Tests

• The bound path, dismissal on the reply, stale and non-stale refusals, and the blind fallbacks are covered in the seam and view suites.
• 5 of the new tests fail against main, and removing the clear(expectedKey) guard fails the in-flight replacement test.
• The affected suites pass: 26 suites, 242 tests.

Refs #841