fix(session): resume loop when user message arrives during question prompt

[TheMrClaus]

Issue for this PR

Closes #46135

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Repro: run the agent until it blocks on an interactive question tool prompt, then submit a new message instead of answering inline. The message gets persisted, but the session never resumes — the engine just hangs with no error.

Root cause: the question tool parks the session run inside Question.ask() on a pending deferred. A new prompt is persisted before the loop is invoked, but because the session is already running the fresh runLoop work is ignored — so the existing run stays stuck in the question wait forever, and nothing ever consumes the new message. No step-finish, no abort, no error event.

Fix: when a fresh prompt is persisted, reject any pending questions for that session. The processor's Question.RejectedError handler then checks whether a newer user message exists; if one does, the loop is allowed to continue — the tool settles, history reloads, and the queued message is processed as the next turn. Dismissing the prompt without a newer message still stops the run, same as before.

How did you verify your code works?

Added a regression test: submit a prompt while a question tool is pending, then submit a second prompt. It asserts both prompt fibers complete, the second user message reaches the next LLM input, the question tool settles to an error state, and the pending-question list drains. Before the fix it hung with "timed out waiting for loop to resume"; after the fix it passes (~3s).

Typecheck (tsgo --noEmit) is clean. I also ran the full package suite: 3353 pass, 43 fail — the failures are pre-existing environment issues on this machine (subprocess tests can't find bare bun on PATH; a host-umask assertion expects 0644 vs 0664), unrelated to this change.

Screenshots / recordings

N/A — not a UI change.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

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