[F139] scope active_task_owns_branch to the polled project

active_task_owns_branch did an unscoped WHERE branch_name = ? — a cross-project
branch_name collision (UUID-derived 8-char prefixes, theoretical) made the
internal-PR reviewer skip the WRONG project's PR (project A's leftover PR
skipped because project B happened to have an active task with the same
branch). Pass project_id (in scope at the orchestrator call site) and add
TaskTable.project_id == project_id to the WHERE. Correct for single-project
tasks and MegaTask multi-repo batches alike: each root-subtask carries its own
project_id matching its own repo, so a branch on project A's repo is owned
only by a task whose project_id == A.

tests/unit/services/test_external_pr_ingest.py

@@ -146,17 +146,18 @@ def _branch_service(*, found: bool) -> TaskService:
 @pytest.mark.asyncio
 async def test_active_task_owns_branch_true_when_live_task_holds_it() -> None:
     assert (
-        await _branch_service(found=True).active_task_owns_branch("feature/x") is True
+        await _branch_service(found=True).active_task_owns_branch("feature/x", uuid4())
+        is True
     )
 
 
 @pytest.mark.asyncio
 async def test_active_task_owns_branch_false_when_no_live_task() -> None:
     svc = _branch_service(found=False)
-    assert await svc.active_task_owns_branch("feature/x") is False
+    assert await svc.active_task_owns_branch("feature/x", uuid4()) is False
 
 
 @pytest.mark.asyncio
 async def test_active_task_owns_branch_false_for_empty_branch() -> None:
     # No branch → cannot be owned; never hits the DB.
-    assert await TaskService(MagicMock()).active_task_owns_branch("") is False
+    assert await TaskService(MagicMock()).active_task_owns_branch("", uuid4()) is False