feat(cli): answer a run's human gate from the terminal

[EdmondDantes]

What

The fourth slice of TODO item 2 (3b), completing the run experience over the server. #93 brought the trace back to the terminal read-only; this makes it interactive — when a tailed run parks at a question, the CLI asks the person and sends their reply, and the run carries on.

• ServerClient::answer() — POST /api/projects/{key}/issues/{id}/answer with {"text": …}, mapping 202→ok, 409→"the run is not waiting" exception, else error.
• WorkflowMode::tailRun() — a question trace row opens the gate (its prompt is the question), an answer row closes it; on a tty the CLI prompts on STDIN and posts the reply, on a pipe it keeps the read-only hint so it never blocks on input.

Behaviour

⏸ Which sort should the module use — merge or quick?
› merge sort

• Answer accepted → the run wakes (the server sends it down the gate channel) and the trace keeps flowing.
• Piped / non-interactive claw run never blocks: it prints the dashboard hint once and keeps following.
• Ctrl-D / closed input detaches cleanly (the run continues on the server; answer it in the dashboard).
• A rejected answer (409 "not waiting" — the gate was answered elsewhere or the run moved on) is dropped, not re-prompted in a loop.

Honesty

answer()'s status mapping is unit-tested. The interactive path is not live-verified — a real gate fires only when the model decides to ask, which is non-deterministic and costs a full run to reach. The read-only tail it builds on was verified live in #93. Reviewed for control-flow (no spin/double-prompt/missed-gate).

Design note

Answering by issue, not by question id: the server matches the reply to the issue's one open gate (POST …/answer takes only text), and has a dead-gate fallback that journals the answer if the run that asked is gone — so a reply is never lost to a restart.

Not in this PR

• /start returning the run id (would remove the awaitRun discovery poll).
• Folding claw -i / -c writers behind the server.

Checks

composer qa green — cs, PHPStan level 8, Testo (459 tests). New tests cover the answer status mapping (accepted carries the text; 409 is surfaced).