Lay out horizontally scaled text in page units

[youdie006]

What kind of change does this PR introduce?

Bug fix. LineWrapper multiplies width, indent and columnGap by horizontalScaling / 100, but widthOfString() already returns scaled widths, so the two cancel out. Text wraps at the same words as at 100%, overflows the box above 100% and leaves it part empty below, and right and center alignment are off by the same factor. Glyph boxes from pdftotext -bbox, width: 200 at x 50 (right edge 250):

	master	this PR
paragraph, horizontalScaling: 150, rightmost glyph	331.7	239.4
paragraph, horizontalScaling: 50, lines	4 (right edge 143.9)	2 (245.3)
'Hello big world', width: 400, align: 'right', horizontalScaling: 80, right margin	80.00	0.00
same with horizontalScaling: 120	-80.00	0.00
align: 'center', horizontalScaling: 120, left / right margin	192.75 / 112.75	152.75 / 152.75
indent: 20, horizontalScaling: 120, first line starts at	74.0	70.0

The wrapper now keeps those three in page units; character and word spacing stay scaled, as Tz scales them. align: 'justify' computed the gap in page units and then let Tz scale it again, so with only the wrapper fixed, justified lines ended at about 259 (120%) or 245 (80%) instead of 250. That gap is now divided by the scaling. The word spacing in the decoration width and in boundsOfString() is scaled as well; for wordSpacing: 6, horizontalScaling: 80 the bounds width is now 72.60, the glyph width, instead of 75.00.

With horizontalScaling left at 100 nothing changes. The new tests in tests/unit/text.spec.js fail on master (8 of them), and reverting either file or any one of the five scaled terms fails at least one. prettier --check, lint and npm test (61 files, 538 tests) pass on Node 22; I did not run Node 20 or 24.

Checklist:

• Unit Tests
• Documentation N/A
• Update CHANGELOG.md
• Ready to be merged

Written with AI assistance (Claude); I have reviewed the change.

[blikblum]

Is there a code snippet that demonstrate the issue visually?

[youdie006]

Yes, this draws a 200pt-wide box and fills it at 50%, 100% and 150%, plus a right-aligned line at 120%:

const PDFDocument = require('pdfkit');
const fs = require('fs');

const doc = new PDFDocument();
doc.pipe(fs.createWriteStream('hscale.pdf'));
const text = 'The quick brown fox jumps over the lazy dog while the five boxing wizards jump quickly';
[50, 100, 150].forEach((horizontalScaling, i) => {
  const y = 50 + i * 120;
  doc.rect(50, y, 200, 100).stroke();
  doc.text(text, 50, y, { width: 200, horizontalScaling });
});
doc.rect(50, 420, 200, 20).stroke();
doc.text('right aligned', 50, 420, { width: 200, align: 'right', horizontalScaling: 120 });
doc.end();

On master the 150% text runs out of the box on every line and the 50% text only fills the left half, because each case breaks at the same words as 100%; the right-aligned line ends 40pt past the box. Rightmost glyph edges from pdftotext -bbox-layout (box right edge at 250):

	master	this PR
50%	143.9 (3 lines)	245.3 (2 lines)
100%	237.8	237.8
150%	331.7 (3 lines)	239.4 (4 lines)
right, 120%	290.0	250.0