feat(tools): add ask_user_question for mid-turn question prompting

[devproje]

What this changes

Every mid-turn round-trip so far was yes/no/deny dangerous-tool approval — there was no way for the model to ask the human an actual question and get an answer back. Adds ask_user_question, a PermissionSafe tool that blocks on the human's reply the same way tool approval already blocks, and returns the answer (a chosen option's text, or free-typed text) as the tool result.

It reuses approvalRouter's pending-channel map instead of adding a second one — one entry per session is safe because SessionLock already limits a session to one in-flight tool call at a time. wait() now takes the value to return on cancellation as a parameter ("deny" for approval, "" for a question) instead of hardcoding "deny", since an unanswered question isn't a denial.

modules/ask_question takes an injected AskFunc closure rather than importing core, mirroring web_search/web_fetch's WebBackendLookup pattern, since core already imports it and a direct import would cycle. The REPL client gains renderer.readLine (Enter submits, Backspace edits, Ctrl+C aborts) built on the same raw-byte primitive the existing y/a/N approval prompt uses, and renderer.ask, which accepts either a numbered option or free-typed text as the answer. The -p --format json/xml path and a nil AskFunc both fail fast instead of hanging, mirroring how approval_request is already auto-denied there.

How it was verified

• make test-race passes
• New behaviour has a test, or there is nothing to test

Added modules/ask_question/ask_question_test.go (missing-question error, nil-AskFunc error, answer round-trip) and server/sock/question_test.go (a full question_request/question round trip over a real websocket connection through the tool loop, mirroring the existing approval round-trip tests in server/sock/hil_test.go).

Checklist

• Follows docs/CONVENTION.md: no comments, no :=, one var block per function in first-use order with err last, callees before callers, and main unconditionally last
• New .go files carry the two-line SPDX header
• Documentation updated if behaviour a user can see has changed (docs/ARCHITECTURE.md)
• My contribution is licensed GPL-3.0-only, matching the project