A buttons widget: a grid of presses on one message

Several stateless instructions where a single button is one — six presets are
otherwise six tiles to place, six titles to read, and the message they share
repeated six times. Nothing is read back, as for a single button: what these
send is an instruction, and the last one sent is not a state to draw.

Auto-fit columns rather than a configured count: a tile is resized in the
editor and scaled again to whatever panel it hangs on, so how many fit is not
something the document can know.

The editor reads `cfg.buttons` raw rather than through `buttonsOf`, which
drops the blanks — a row being typed into is blank until the first keystroke.

Also carried along by the hooks: the generated SDK was stale (it had no
`RunsReadMetricNames`) and one pre-existing block in `test_panels.py` was
unformatted.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016bm2HwnRsTDpeWjSPNJxQd

backend/tests/api/routes/test_panels.py

@@ -255,6 +255,14 @@ PANEL_WIDGETS = [
     },
     {"id": "w_input", "type": "input", "config": {"target": "demo.input"}},
     {"id": "w_dropdown", "type": "dropdown", "config": {"target": "demo.dropdown"}},
+    {
+        "id": "w_buttons",
+        "type": "buttons",
+        "config": {
+            "target": "demo.buttons",
+            "buttons": [{"label": "One", "value": 1}],
+        },
+    },
     {
         "id": "w_query",
         "type": "chart",
@@ -313,6 +321,7 @@ def test_a_panel_speaks_only_its_own_widgets_messages(
         "demo.slider",
         "demo.input",
         "demo.dropdown",
+        "demo.buttons",
         "demo.query_request",
     ):
         assert (
@@ -854,8 +863,9 @@ def test_a_socket_pushes_only_the_frames_it_was_asked_for(tmp_path) -> None:
 
     store = ArtifactStore(tmp_path / "artifacts")
     store.volatile = VolatileStore(tmp_path / "ring", limit_bytes=1_000_000)
-    frame = store.put([b"\x89PNG..."], name="f.png", media_type="image/png",
-                      volatile=True)
+    frame = store.put(
+        [b"\x89PNG..."], name="f.png", media_type="image/png", volatile=True
+    )
     kept = store.put([b"checkpoint"], name="w.pt")
 
     asking = orjson.dumps({"type": "media", "names": ["cam.frame", "other.frame"]})