test(deck): address PR #872 round-2 review

- Assert the open card stays visible under status="open" in the
  deck_get_stack integration test (completes the partition check).
- Move the _append_archived_cards docstring closing quotes to their own line.

deck_get_stack's status="archived" + include_cards=False path is left as-is:
a single get_stack call is the cheapest way to obtain the stack metadata
there — routing it through the archived fast-path would fetch every archived
stack on the board just to strip the cards, which is heavier, not lighter.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/server/test_deck_mcp.py

@@ -505,7 +505,9 @@ async def test_deck_get_stack_status_includes_archived_mcp(
         payload = json.loads(result.content[0].text)
         return [c["id"] for c in (payload.get("cards") or [])]
 
-    assert archived_id not in await stack_card_ids("open")
+    open_ids = await stack_card_ids("open")
+    assert card_data["id"] in open_ids, "open card must stay visible under 'open'"
+    assert archived_id not in open_ids
     assert archived_id in await stack_card_ids("all")
     assert await stack_card_ids("archived") == [archived_id]