tui: don't let a dead host-key prompt hold the keyboard

[ralyodio]

Reported as: "once it syncs i can't get back to previous screen in tui" — after a sync to a remote endpoint (dev:me).

What was happening

The host-key prompt owns the keyboard while it is up, which is correct — a fingerprint should not be dismissable by mashing keys. What made that dangerous is that it could outlive the connection that asked.

Point a pane at a host DiskPush has not seen, then take fifteen seconds to actually compare the fingerprint. ssh2's readyTimeout (connectTimeoutSeconds, 15s) fires, SshSession.connect rejects with "Timed out while waiting for handshake", the pane shows that error — and this.hostKey is never cleared. The question stays on screen with nobody behind it.

From then on every key lands in this branch:

if (this.hostKey) {
  if (isChar(key, 'y') || ...) this.hostKey.decide(true)
  else if (key === 'escape' || ...) this.hostKey.decide(false)
  return true          // <- q lands here too
}

decide resolves a promise nobody awaits, so answering does nothing useful — and because the branch only ever returns true, q never quits. Arrows do nothing, panes never move, and Ctrl-C is the only way out. The app looks frozen because it is.

It reads as a sync bug because the post-sync reload is what re-enters session() and raises the question again.

The fix

Two changes, neither of which loosens the prompt:

• session() clears the question in a finally. Whoever asked is gone, so the question goes with them. On the success path this is already null (decide clears it), so it is a no-op there.
• q quits from inside the prompt. Everything else is still deliberately swallowed — an arrow must not leak through to the panes behind it — but a dialog that can trap you in the app is worse than one you can leave, and q is the quit key everywhere else.

How it was found and confirmed

By driving the real TUI over a pty against a real sshd, counting redraws (every frame starts with ESC[2J) and reading the last frame back. That is what showed the tell: the pane said "Timed out while waiting for handshake" and the "Unknown host" box was still drawn underneath it.

Same harness, before and after:

	before	after
TAB / j / h after the failed connect	frames increment, screen never changes	marker moves, pane goes up a directory
q	does not exit — process must be killed	exits cleanly

apps/cli/src/tui/host-key-prompt.test.ts adds 3 tests. The two that pin the fix fail without it; the third — y/n still answer, other keys still swallowed — passes either way, which is what makes it a regression test rather than a restatement.

Full suite: 238 tests, all passing.

🤖 Generated with Claude Code

https://claude.ai/code/session_01Y5jnkZKX4AdPgBMzMosxE7