Trim needless comments and fix the picker width

Remove comments that only restate the code, keeping the section banners
and the notes that carry a reason, a measured fact or an external
contract.

ButtonOptions.width claimed to be a fixed width but only set minWidth,
so the Graph and Texture pickers grew with the name they showed. It is
now what it promises, with a separate minWidth for the buttons that have
two forms. Narrow buttons shrink their padding, otherwise a 24px icon
button had 8px left for its glyph and truncate dropped it entirely.

__gm.labelsDropped() guards that class: the overflow guard only saw text
that was too wide, never a label truncated to nothing.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tools/e2e/06-graph.mjs

@@ -186,9 +186,8 @@ export async function graph(t) {
   await undo();
   check('undo removes the variable', (await variableKeys()) === 'speed', await variableKeys());
 
-  // 13h. The tab keeps its subject. A selection about something else (nothing, a camera) leaves
-  //      the graph alone – clicking a sprite to look at it must not empty the editor you are
-  //      working in – and the header picker switches behaviors without any selection at all.
+  // 13h. The tab keeps its subject: selecting something else leaves the graph alone, and the
+  //      header picker switches behaviors without any selection at all.
   const size = await graphCounts();
   const readout = `${size.nodes} nodes · ${size.edges} links`;
   check(
@@ -208,8 +207,7 @@ export async function graph(t) {
     'graph editor keeps its behavior for a non-behavior asset',
     (await evaluate(`__gm.graph.current()`)) === 'mover',
   );
-  // The picker is the *last* "Mover" on screen: the assets panel shows one too, and the
-  // inspector is on the camera.
+  // The picker is the *last* "Mover" on screen: the assets panel shows one too.
   const pickerAt = await locate('Mover', true);
   await click(pickerAt.x, pickerAt.y);
   await sleep(150);