* fix(core): let fill text share an auto-layout row
Fill frames grow and shrink from a zero flex basis, so fill siblings split a row's free space. Fill text only got flexGrow, and its measure function capped it at its stored width, 100px for new text, so seven fill labels in a 280px row each kept 100px and overflowed. Without a measurer, the fallback pinned that width and set no grow at all. Fill text now uses the same zero basis as fill frames on both paths.
* fix(design-jsx): read repeat() and minmax() in grid tracks
Track lists were split on whitespace, so columns="repeat(7, 1fr)" became the tracks repeat(7, and 1fr), read as fixed 0px and 1px columns that collapsed the grid. Tokens inside parentheses now stay together, repeat() expands its tracks, minmax() grows like its maximum, and a track the grid cannot express sizes to its content instead of to 0.
* refactor(scene-graph): parse CSS grid tracks with postcss-value-parser
design-jsx read repeat() and minmax() with a hand-written tokenizer and regexes, while dom-css already parses CSS values with postcss-value-parser. Track lists are now parsed in @open-pencil/scene-graph/css on that library, where both packages can use it, and design-jsx calls it. dom-css's hand-written declaration of the library's types is replaced by the types the library ships, which the shared module needs. The Scene Graph guide records that CSS values are parsed there.
* fix(dom-css): read shadows, borders, and lengths with the shared CSS parser
dom-css tried each word of a shadow as a color and parseColor turned the leading 0 into black, so a shadow written in the usual order imported black, and the headless runtime split the border shorthand on spaces, which cut rgb(226, 232, 240) apart and also gave a black border. Numbers, colors, shadow lists, and shorthand parts are now parsed in @open-pencil/scene-graph/css on postcss-value-parser. Every shadow layer imports, inset ones as inner shadows, a fully transparent color counts as none, and lengths in units that depend on context, such as % or em, are no longer read as pixels. tryParseColor gives the color or null, and parseColor builds on it.
* fix(design-jsx): read the shadow prop as a CSS shadow list
The shadow prop was split on spaces, so a color before the lengths or a spread made the shadow black, and only one shadow could be set. It now takes a CSS box-shadow list through the shared parser, and pixel lengths in style props use the shared number parser. A rem grid track now has its size instead of sizing to content.
* test: type grid track and shadow fixtures
The test type check added in #896 rejects the grid track tests that #866 merged, because their object literals widen sizing to string, so bun run check fails on master. The fixtures are now typed GridTrack and Effect values.