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, 44 insertions, 0 deletions

diff --git a/web/style.css b/web/style.css
index 1478b36..91466ee 100644
--- a/web/style.css
+++ b/web/style.css
@@ -8,6 +8,7 @@
   --state-timed-out:        #c084fc;
   --state-cancelled:        #9ca3af;
   --state-budget-exceeded:  #fb923c;
+  --state-blocked:          #818cf8;
 
   --bg:          #0f172a;
   --surface:     #1e293b;
@@ -181,6 +182,7 @@ main {
 .state-badge[data-state="TIMED_OUT"]        { background: var(--state-timed-out); }
 .state-badge[data-state="CANCELLED"]        { background: var(--state-cancelled); }
 .state-badge[data-state="BUDGET_EXCEEDED"]  { background: var(--state-budget-exceeded); }
+.state-badge[data-state="BLOCKED"]          { background: var(--state-blocked); }
 
 /* Task meta */
 .task-meta {
@@ -294,6 +296,48 @@ main {
   cursor: not-allowed;
 }
 
+.task-question-text {
+  font-size: 0.82rem;
+  color: var(--text);
+  margin: 0 0 0.5rem 0;
+  line-height: 1.4;
+  width: 100%;
+}
+
+.task-answer-row {
+  display: flex;
+  gap: 0.375rem;
+  width: 100%;
+}
+
+.task-answer-input {
+  flex: 1;
+  font-size: 0.8rem;
+  padding: 0.3em 0.6em;
+  border-radius: 0.375rem;
+  border: 1px solid var(--border);
+  background: var(--bg);
+  color: var(--text);
+}
+
+.btn-answer {
+  font-size: 0.8rem;
+  font-weight: 600;
+  padding: 0.35em 0.85em;
+  border-radius: 0.375rem;
+  border: none;
+  cursor: pointer;
+  background: var(--state-blocked);
+  color: #0f172a;
+  transition: opacity 0.15s;
+  margin-right: 0.375rem;
+}
+
+.btn-answer:disabled {
+  opacity: 0.5;
+  cursor: not-allowed;
+}
+
 .task-error {
   font-size: 0.78rem;
   color: var(--state-failed);