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/fluksio/flow/dashboards.py

@@ -68,6 +68,7 @@ WidgetType = Literal[
     "embed",
     # Input
     "button",
+    "buttons",
     "switch",
     "slider",
     "input",
@@ -78,7 +79,15 @@ WidgetType = Literal[
 #: Widgets whose only binding is the message they publish. A player is not one:
 #: it publishes transport commands *and* reads what is playing, so its reading
 #: is its binding and its ``target`` is checked separately.
-INPUT_WIDGETS = {"button", "switch", "slider", "input", "dropdown", "color"}
+INPUT_WIDGETS = {
+    "button",
+    "buttons",
+    "switch",
+    "slider",
+    "input",
+    "dropdown",
+    "color",
+}
 
 #: What a colour widget puts on the wire, by the format it was configured for.
 #: The default is what the Node-RED instance this ports already sends its