feat(prompter): make the intake actually use its task-history digest (#592)

The history-digest pipeline (PR #297) injected past-task data but nothing
told the intake agent what to do with it: prompter.md now carries an
explicit don't-re-propose section (cite duplicates by short id, reference
precedent in notes, let history inform depends_on sequencing), and
list_recent_for_project excludes cancelled tasks so dead work can't pose
as precedent.

Co-authored-by: Renn F <rennf93@users.noreply.github.com>

tests/integration/test_task_service_basics.py

@@ -321,6 +321,21 @@ async def test_list_recent_for_project_scoped_to_project(
     assert out_of_scope.id not in ids
 
 
+@pytest.mark.asyncio
+async def test_list_recent_for_project_excludes_cancelled(task_setup: dict) -> None:
+    svc = task_setup["svc"]
+    db = task_setup["db"]
+    live = await svc.create(_req(task_setup, title="live"))
+    cancelled = await svc.create(_req(task_setup, title="cancelled"))
+    cancelled.status = TaskStatus.CANCELLED
+    await db.flush()
+
+    rows = await svc.list_recent_for_project(task_setup["project_id"])
+    ids = {t.id for t in rows}
+    assert live.id in ids
+    assert cancelled.id not in ids
+
+
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 # Subtask hierarchy
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