fix(console): available-models rows always carry effort_ladder

The except path for a malformed capabilities column appended the row
without the key, so clients had to null-check a field the happy path
guarantees. Initialize each entry with an empty ladder and let the try
block overwrite it — the response schema is stable per row.

tests/test_console_available_models.py

@@ -372,6 +372,30 @@ def test_effort_ladder_parses_string_capabilities(storage: SQLiteBackend) -> Non
     assert ladder["max"] == "on"
 
 
+def test_effort_ladder_key_survives_malformed_capabilities(
+    storage: SQLiteBackend,
+) -> None:
+    """A capabilities column that fails to parse must not drop the key —
+    every row carries ``effort_ladder`` (empty on failure) so clients can
+    index it unconditionally instead of null-checking per row."""
+    storage.create_model_definition(
+        definition_id="m1",
+        alias="broken",
+        model="model-x",
+        provider="openai-compatible",
+        base_url="http://localhost:8000/v1",
+        api_key="dummy",
+        context_window=131072,
+        capabilities="{not valid json",
+        enabled=True,
+        created_by="admin",
+    )
+    body = _get_models(_make_client(storage))
+    entry = body["models"][0]
+    assert set(entry) == {"alias", "model", "provider", "effort_ladder"}
+    assert entry["effort_ladder"] == []
+
+
 def test_effort_ladder_honors_responses_api_surface(storage: SQLiteBackend) -> None:
     """server_compat.api_surface (namespaced inside the capabilities JSON)
     switches the projection to the flat-param path — no template toggle."""

turnstone/console/server.py

@@ -1916,10 +1916,14 @@ async def list_available_models(request: Request) -> JSONResponse:
 
     models = []
     for r in rows:
+        # ``effort_ladder`` starts as the empty list so the row schema is
+        # stable even when the try block below bails on a malformed
+        # capabilities column — clients can index the key unconditionally.
         entry: dict[str, Any] = {
             "alias": r["alias"],
             "model": r["model"],
             "provider": r["provider"],
+            "effort_ladder": [],
         }
         try:
             # ``capabilities`` is a JSON string (sa.Text column) with