Redraw every icon on the pixel grid it renders at

On a 1x screen TDesign's glyphs smeared at 14 and 16px: their 24-unit
strokes land between pixels, so every ~1px line covered two at half ink.
All 37 icon/size pairs are now TDesign's shapes redrawn on their own grid
(viewBox 0 0 N N, so one unit is one CSS pixel):

- Straight lines are runs of whole pixels that end on pixel edges, with
  no caps or joins. WebKit drops square caps on a path of several
  subpaths, and Skia strokes 1px lines as hairlines that leave a joined
  corner pixel three-quarters inked.
- Slants and curves are 1.25px so they read as heavy as the crisp runs.
  Their ends, vertices and circle extremes sit on pixel centres.
- server24 keeps TDesign's 24px geometry; only its dots move onto whole
  pixels.

Only closeCircle24 (TDesign's own 24px grid) and the spinner still come
from @ng-icons/tdesign-icons. This also fixes add14 from 5d23809, whose
square-capped ends rendered half-inked in WebKit. icons.spec.ts now also
checks that every grid name's glyph uses that grid's viewBox.

Checked at 1x and 2x in WebKit (the app's macOS engine) and in Chrome
(Skia, as in WebView2 and WebKitGTK); straight runs fill whole pixels in
both. In WebKit at 1x, a copy of the tab bar, toolbar, file rows, menu
and shortcut-row markup rendered every straight-line glyph with zero
blur, including icons laid out on fractional pixels.

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

ui/src/app/core/icons.spec.ts

@@ -1,5 +1,6 @@
 import { expect, test } from 'bun:test';
 import { APP_ICONS } from './icons';
+import { PIXEL_ICONS } from './pixel-icons';
 
 // The px grid of each size token (styles.css); lg only carries the spinner.
 const GRID: Record<string, string> = { sm: '14', md: '16', lg: '20', xl: '24' };
@@ -31,3 +32,18 @@ test('every template icon is registered and drawn for the size it renders at', a
   }
   expect(problems).toEqual([]);
 });
+
+// A grid name's glyph is drawn on that grid (a TDesign glyph registered as
+// foo14 would be a 24-unit viewBox), and the redrawn ones use plain attributes
+// only: TDesign's stroke-width var or any style would bypass the grid.
+test('every glyph is drawn on the grid its name says', () => {
+  const problems: string[] = [];
+  for (const [name, svg] of Object.entries(APP_ICONS)) {
+    const grid = name.match(/(\d+)$/)?.[1];
+    if (grid && !svg.includes(`viewBox="0 0 ${grid} ${grid}"`)) problems.push(`${name}: not drawn on a ${grid}px grid`);
+  }
+  for (const [name, svg] of Object.entries(PIXEL_ICONS)) {
+    if (/var\(|style=/.test(svg)) problems.push(`${name}: uses a CSS var or a style`);
+  }
+  expect(problems).toEqual([]);
+});