feat: blocked task state for agent questions via session resume

When an agent needs user input it writes a question to
$CLAUDOMATOR_QUESTION_FILE and exits. The runner detects the file and
returns BlockedError; the pool transitions the task to BLOCKED and
stores the question JSON on the task record.

The user answers via POST /api/tasks/{id}/answer. The server looks up
the claude session_id from the most recent execution and submits a
resume execution (claude --resume <session-id> "<answer>"), freeing the
executor slot entirely while waiting.

Changes:
- task: add StateBlocked, transitions RUNNING→BLOCKED, BLOCKED→QUEUED
- storage: add session_id to executions, question_json to tasks;
  add GetLatestExecution and UpdateTaskQuestion methods
- executor: BlockedError type; ClaudeRunner pre-assigns --session-id,
  sets CLAUDOMATOR_QUESTION_FILE env var, detects question file on exit;
  buildArgs handles --resume mode; Pool.SubmitResume for resume path
- api: handleAnswerQuestion rewritten to create resume execution
- preamble: add question protocol instructions for agents
- web: BLOCKED state badge (indigo), question text + option buttons or
  free-text input with Submit on the task card footer

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 76 insertions, 1 deletions

diff --git a/web/app.js b/web/app.js
index 20d7a03..271a18e 100644
--- a/web/app.js
+++ b/web/app.js
@@ -71,7 +71,7 @@ function createTaskCard(task) {
 
   // Footer: action buttons based on state
   const RESTART_STATES = new Set(['FAILED', 'TIMED_OUT', 'CANCELLED']);
-  if (task.state === 'PENDING' || task.state === 'RUNNING' || task.state === 'READY' || RESTART_STATES.has(task.state)) {
+  if (task.state === 'PENDING' || task.state === 'RUNNING' || task.state === 'READY' || task.state === 'BLOCKED' || RESTART_STATES.has(task.state)) {
     const footer = document.createElement('div');
     footer.className = 'task-card-footer';
 
@@ -110,6 +110,8 @@ function createTaskCard(task) {
       });
       footer.appendChild(acceptBtn);
       footer.appendChild(rejectBtn);
+    } else if (task.state === 'BLOCKED') {
+      renderQuestionFooter(task, footer);
     } else if (RESTART_STATES.has(task.state)) {
       const btn = document.createElement('button');
       btn.className = 'btn-restart';
@@ -312,6 +314,79 @@ async function restartTask(taskId) {
   return res.json();
 }
 
+function renderQuestionFooter(task, footer) {
+  let question = { text: 'Waiting for your input.', options: [] };
+  if (task.question) {
+    try { question = JSON.parse(task.question); } catch {}
+  }
+
+  const questionEl = document.createElement('p');
+  questionEl.className = 'task-question-text';
+  questionEl.textContent = question.text;
+  footer.appendChild(questionEl);
+
+  if (question.options && question.options.length > 0) {
+    question.options.forEach(opt => {
+      const btn = document.createElement('button');
+      btn.className = 'btn-answer';
+      btn.textContent = opt;
+      btn.addEventListener('click', (e) => {
+        e.stopPropagation();
+        handleAnswer(task.id, opt, footer);
+      });
+      footer.appendChild(btn);
+    });
+  } else {
+    const row = document.createElement('div');
+    row.className = 'task-answer-row';
+    const input = document.createElement('input');
+    input.type = 'text';
+    input.className = 'task-answer-input';
+    input.placeholder = 'Your answer…';
+    const btn = document.createElement('button');
+    btn.className = 'btn-answer';
+    btn.textContent = 'Submit';
+    btn.addEventListener('click', (e) => {
+      e.stopPropagation();
+      if (input.value.trim()) handleAnswer(task.id, input.value.trim(), footer);
+    });
+    input.addEventListener('keydown', (e) => {
+      if (e.key === 'Enter' && input.value.trim()) {
+        e.stopPropagation();
+        handleAnswer(task.id, input.value.trim(), footer);
+      }
+    });
+    row.append(input, btn);
+    footer.appendChild(row);
+  }
+}
+
+async function handleAnswer(taskId, answer, footer) {
+  const btns = footer.querySelectorAll('button, input');
+  btns.forEach(el => { el.disabled = true; });
+  const prev = footer.querySelector('.task-error');
+  if (prev) prev.remove();
+
+  try {
+    const res = await fetch(`${API_BASE}/api/tasks/${taskId}/answer`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ answer }),
+    });
+    if (!res.ok) {
+      const body = await res.json().catch(() => ({}));
+      throw new Error(body.error || `HTTP ${res.status}`);
+    }
+    await poll();
+  } catch (err) {
+    btns.forEach(el => { el.disabled = false; });
+    const errEl = document.createElement('span');
+    errEl.className = 'task-error';
+    errEl.textContent = `Failed: ${err.message}`;
+    footer.appendChild(errEl);
+  }
+}
+
 async function handleCancel(taskId, btn, footer) {
   btn.disabled = true;
   btn.textContent = 'Cancelling…';