Stop a full-width checkbox putting a scrollbar inside the card

ipywidgets checkboxes carry their own padding and a minimum width, so
`width="100%"` overflows the container and leaves a horizontal scrollbar under
the row -- visible under "Allow paid GPU flavors" in the HuggingFace section.
They size to their content now.

Adds docs/evidence/widget/05-huggingface-jobs.jpg, showing the HuggingFace
Jobs section that the widget gained in this branch.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012gTBDPK16HUZ3kHQ2QyjuU

Author: jeremymanning

clustrix/modern_notebook_widget.py

@@ -175,6 +175,13 @@ def _inject_css_styles(self) -> None:
         .clustrix-widget .widget-hbox,
         .clustrix-widget .widget-vbox { min-width: 0 !important; }
         .clustrix-row { max-width: 100%; overflow: hidden; }
+        /* ipywidgets checkboxes carry their own padding and a min-width that
+           together overflow a full-width container, leaving a scrollbar. */
+        .clustrix-widget .widget-checkbox {
+            width: auto !important;
+            max-width: 100%;
+            overflow: hidden;
+        }
         .clustrix-section { margin-bottom: 16px !important; }
         .clustrix-section:last-child { margin-bottom: 0 !important; }
 
@@ -965,7 +972,7 @@ def _create_remote_section(self) -> None:
             value=False,
             description="Allow paid GPU flavors",
             indent=False,
-            layout=widgets.Layout(width="100%"),
+            layout=widgets.Layout(width="auto", margin="4px 0 0 0"),
         )
 
         hf_row = widgets.HBox(