Changelog: say what scaleRounding is, in two sentences

[obiot]

The scaleRounding entry ran to four sentences and 756 characters, twice the
length of anything near it in the 20.9 section, and still never said the thing
a reader needs first: that this is a new optional application setting
whose default changes nothing.

Before:

scaleRounding: "integer" constrains the automatic scale factor to a
whole number of device pixels per source pixel, letterboxing whatever is left
over, where the default "fractional" fills the container exactly. A 480
wide design in a 1280 wide container is scaled by 2.667, so some source
pixels cover three device pixels and some cover two, which pixel art shows as
uneven stems and shimmering edges and which browsers resolve differently, so
the same scene looks crisp in one and soft in another. The rounding is
applied in DEVICE pixels, since devicePixelRatio would otherwise put the
fraction back. It affects scaleMethod: "fit" only, because every other
method resizes the renderer to its container and so has no fixed factor to
round

After:

scaleRounding application setting: optional, and "fractional" by
default, so nothing existing changes. "integer" constrains the automatic
scale factor to a whole number of device pixels per source pixel and
letterboxes the remainder, which is what stops pixel art showing uneven stems
and shimmering edges; it applies to scaleMethod: "fit" only

358 characters, two sentences, in line with its neighbours, and led by
**scaleRounding application setting** the way textureFilter was introduced
in 19.8.

Three things dropped as not actionable: the 480-in-1280 worked example, the
browser-to-browser comparison, and the note that rounding happens in device
pixels. The first two are in the display and scaling skill, next to the table
of what integer scaling actually costs; the last is a correctness property a
reader cannot act on, and is pinned by a test rather than prose.

Worth landing before the tag: the section carries a date, but melonjs is
still unpublished on npm, so this is not retrofitting a released section.

🤖 Generated with Claude Code

https://claude.ai/code/session_01NGvtaUNATVCVxD2qcbiY4t

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