Put the text and boxes of the interface on device pixels

On a screen scaled to 125 % or 150 % the editor looked soft beside
a page the browser draws itself. The layout counts in whole CSS
pixels, and most of those fall between two device pixels there. The
GPU averages both: text loses its edges, and a 1 px line becomes a
pixel and a half of mixed colour. Now text and boxes are rounded to
device pixels, and a line is one device pixel wide.

- ui/pixelGrid.ts holds the rule. crispText() makes a text with
  Pixi's roundPixels, crisp() does the same for a Graphics of
  upright boxes, and hairline() is the width of one device pixel.
- Every text of the interface is made with crispText() instead of
  new Text().
- crisp() only rounds where the scale is not a whole number. At
  100 % and 200 % nothing changes.
- drawControlBox, drawHeaderBar and drawSectionBand draw their
  lines a hairline wide and flush with the edge. The widgets that
  draw lines of their own do the same.
- Two bands share exactly the line they draw, and a column still
  ends on a whole pixel.
- The stage is nudged by 1/32 px where the scale is not whole. At
  150 % every odd pixel is an exact half, and without the nudge one
  band came out a row shorter than its neighbours.
- Curves, icons and everything of the game stay unrounded. Rounding
  their points would bend them.
- The harness takes deviceScaleFactor as an option, and the hooks
  deviceColumn, edgeContrast and pixelGrid read the frame as the
  screen gets it.

Not in here: the subpixel smoothing a browser gives its own text.
Pixi draws a text into a transparent picture first, and there only
greyscale smoothing is possible.

Measured at 150 %, edge contrast before and after: top bar 31.5 to
47.8, the lists on the left 68.6 to 86.4, inspector 27.6 to 38.4.
At 100 % it is 46.5, 90.1 and 37.9, and the picture there is the
same as before pixel for pixel, apart from the fps display.

Tests:
- Gate on melektaus-atx: 206 files, 3114 tests (3104 + 10), exit 0
- Full run on melektaus-atx: 1655 of 1656 checks passed, smokes
  24/19/21. The one that failed was a condition of the new step
  62 itself: it scrolled an inspector that had nothing to scroll.
  The step now makes the window lower for that reading.
- e2e 61,62 after that fix: 14 checks. The full run was not
  repeated, and CI is switched off for now.
- Ten unit tests, nine in tests/ui/pixel-grid.test.ts
- Eight e2e checks in the new step 62, which runs at 150 %
- Eleven unit counter-probes fail tests
- Four browser counter-probes fail their checks. They ran before
  the fix to step 62 and were not repeated for it.
- Screenshots looked at for 125 % and 150 %

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/editor/sections.test.ts

@@ -95,6 +95,13 @@ describe('where bands and rows go', () => {
     expect(height).toBe(ys[2]! + SECTION_BAND_HEIGHT);
   });
 
+  it('shares exactly the line the bands draw, and still ends on a whole pixel', () => {
+    const line = 2 / 3;
+    const { ys, height } = sectionOffsets([band, band], GAP, PADDING, line);
+    expect(ys[1]).toBeCloseTo(SECTION_BAND_HEIGHT - line, 10);
+    expect(height).toBe(Math.ceil(2 * SECTION_BAND_HEIGHT - line));
+  });
+
   it('starts inside the padding without a band on top', () => {
     expect(sectionOffsets([plain, plain], GAP, PADDING).ys).toEqual([PADDING, PADDING + 24 + GAP]);
   });