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, 68 insertions, 0 deletions

diff --git a/internal/storage/db_test.go b/internal/storage/db_test.go
index 4f9069a..395574c 100644
--- a/internal/storage/db_test.go
+++ b/internal/storage/db_test.go
@@ -421,3 +421,71 @@ func TestUpdateExecution(t *testing.T) {
 		t.Errorf("artifact_dir: want /tmp/exec, got %q", got.ArtifactDir)
 	}
 }
+
+func makeTestTask(id string, now time.Time) *task.Task {
+	return &task.Task{
+		ID: id, Name: "T-" + id, Claude: task.ClaudeConfig{Instructions: "x"},
+		Priority: task.PriorityNormal, Retry: task.RetryConfig{MaxAttempts: 1, Backoff: "linear"},
+		Tags: []string{}, DependsOn: []string{},
+		State: task.StatePending, CreatedAt: now, UpdatedAt: now,
+	}
+}
+
+func TestStorage_SessionID_RoundTrip(t *testing.T) {
+	db := testDB(t)
+	now := time.Now().UTC()
+	db.CreateTask(makeTestTask("sid-task", now))
+
+	exec := &Execution{
+		ID: "sid-exec", TaskID: "sid-task", StartTime: now, Status: "RUNNING",
+		SessionID: "550e8400-e29b-41d4-a716-446655440000",
+	}
+	if err := db.CreateExecution(exec); err != nil {
+		t.Fatalf("create: %v", err)
+	}
+
+	got, err := db.GetExecution("sid-exec")
+	if err != nil {
+		t.Fatalf("get: %v", err)
+	}
+	if got.SessionID != exec.SessionID {
+		t.Errorf("session_id: want %q, got %q", exec.SessionID, got.SessionID)
+	}
+}
+
+func TestStorage_UpdateTaskQuestion(t *testing.T) {
+	db := testDB(t)
+	now := time.Now().UTC()
+	tk := makeTestTask("q-task", now)
+	db.CreateTask(tk)
+
+	q := `{"text":"Which branch?","options":["main","develop"]}`
+	if err := db.UpdateTaskQuestion("q-task", q); err != nil {
+		t.Fatalf("update question: %v", err)
+	}
+
+	got, err := db.GetTask("q-task")
+	if err != nil {
+		t.Fatalf("get: %v", err)
+	}
+	if got.QuestionJSON != q {
+		t.Errorf("question_json: want %q, got %q", q, got.QuestionJSON)
+	}
+}
+
+func TestStorage_GetLatestExecution(t *testing.T) {
+	db := testDB(t)
+	now := time.Now().UTC()
+	db.CreateTask(makeTestTask("le-task", now))
+
+	db.CreateExecution(&Execution{ID: "le-1", TaskID: "le-task", StartTime: now, Status: "COMPLETED"})
+	db.CreateExecution(&Execution{ID: "le-2", TaskID: "le-task", StartTime: now.Add(time.Minute), Status: "RUNNING"})
+
+	got, err := db.GetLatestExecution("le-task")
+	if err != nil {
+		t.Fatalf("get latest: %v", err)
+	}
+	if got.ID != "le-2" {
+		t.Errorf("want le-2, got %q", got.ID)
+	}
+}