fix(kanban): preserve scratch completion artifacts

tests/hermes_cli/test_kanban_db.py

@@ -2363,6 +2363,125 @@ def test_cleanup_workspace_removes_managed_scratch_dir(kanban_home):
     assert not ws.exists(), "Hermes-managed scratch dir should be cleaned up"
 
 
+def test_complete_task_persists_scratch_artifacts_before_cleanup(kanban_home):
+    """Completion artifacts from scratch workspaces survive workspace cleanup."""
+    with kb.connect() as conn:
+        t = kb.create_task(conn, title="render chart")
+        task = kb.get_task(conn, t)
+        ws = kb.resolve_workspace(task)
+        kb.set_workspace_path(conn, t, ws)
+        artifact = ws / "chart.png"
+        artifact.write_bytes(b"png-bytes")
+
+        assert kb.complete_task(
+            conn,
+            t,
+            result="ok",
+            metadata={"artifacts": [str(artifact)]},
+        )
+
+        completed = [e for e in kb.list_events(conn, t) if e.kind == "completed"][-1]
+        persisted = Path(completed.payload["artifacts"][0])
+        run = kb.latest_run(conn, t)
+
+    assert not ws.exists(), "scratch workspace should still be cleaned up"
+    assert persisted.exists(), "artifact copy should survive scratch cleanup"
+    assert persisted.parent == kb.task_attachments_dir(t)
+    assert persisted.name == "chart.png"
+    assert persisted.read_bytes() == b"png-bytes"
+    assert str(persisted) != str(artifact)
+    assert run is not None
+    assert run.metadata["artifacts"] == [str(persisted)]
+
+
+def test_complete_task_leaves_non_scratch_artifact_paths_unchanged(
+    kanban_home,
+    tmp_path,
+):
+    """Only artifacts inside the managed scratch workspace are copied."""
+    external = tmp_path / "report.md"
+    external.write_text("keep me here", encoding="utf-8")
+
+    with kb.connect() as conn:
+        t = kb.create_task(conn, title="external report")
+        task = kb.get_task(conn, t)
+        ws = kb.resolve_workspace(task)
+        kb.set_workspace_path(conn, t, ws)
+
+        assert kb.complete_task(
+            conn,
+            t,
+            result="ok",
+            metadata={"artifacts": [str(external)]},
+        )
+
+        completed = [e for e in kb.list_events(conn, t) if e.kind == "completed"][-1]
+        run = kb.latest_run(conn, t)
+
+    assert not ws.exists(), "scratch workspace should still be cleaned up"
+    assert external.exists()
+    assert completed.payload["artifacts"] == [str(external)]
+    assert run is not None
+    assert run.metadata["artifacts"] == [str(external)]
+
+
+def test_complete_task_persists_duplicate_scratch_artifact_names(kanban_home):
+    """Scratch artifact persistence does not overwrite duplicate basenames."""
+    with kb.connect() as conn:
+        t = kb.create_task(conn, title="render reports")
+        task = kb.get_task(conn, t)
+        ws = kb.resolve_workspace(task)
+        kb.set_workspace_path(conn, t, ws)
+        first = ws / "a" / "report.txt"
+        second = ws / "b" / "report.txt"
+        first.parent.mkdir(parents=True)
+        second.parent.mkdir(parents=True)
+        first.write_text("first", encoding="utf-8")
+        second.write_text("second", encoding="utf-8")
+
+        assert kb.complete_task(
+            conn,
+            t,
+            result="ok",
+            metadata={"artifacts": [str(first), str(second)]},
+        )
+
+        completed = [e for e in kb.list_events(conn, t) if e.kind == "completed"][-1]
+        persisted = [Path(p) for p in completed.payload["artifacts"]]
+
+    assert not ws.exists(), "scratch workspace should still be cleaned up"
+    assert [p.name for p in persisted] == ["report.txt", "report_1.txt"]
+    assert [p.read_text(encoding="utf-8") for p in persisted] == ["first", "second"]
+    assert all(p.parent == kb.task_attachments_dir(t) for p in persisted)
+
+
+def test_complete_task_persists_board_scratch_artifacts_to_board_attachments(kanban_home):
+    """Board scratch artifacts are copied under that board's attachment root."""
+    kb.create_board("work-proj")
+
+    with kb.connect(board="work-proj") as conn:
+        t = kb.create_task(conn, title="board chart", board="work-proj")
+        task = kb.get_task(conn, t)
+        ws = kb.resolve_workspace(task, board="work-proj")
+        kb.set_workspace_path(conn, t, ws)
+        artifact = ws / "chart.png"
+        artifact.write_bytes(b"board-png")
+
+        assert kb.complete_task(
+            conn,
+            t,
+            result="ok",
+            metadata={"artifacts": [str(artifact)]},
+        )
+
+        completed = [e for e in kb.list_events(conn, t) if e.kind == "completed"][-1]
+        persisted = Path(completed.payload["artifacts"][0])
+
+    assert not ws.exists(), "board scratch workspace should still be cleaned up"
+    assert persisted.exists()
+    assert persisted.parent == kb.task_attachments_dir(t, board="work-proj")
+
+
 def test_cleanup_workspace_refuses_path_outside_scratch_root(kanban_home, tmp_path):
     """A scratch task with a user path outside the workspaces root must NOT be deleted (#28818).