[eslint-plugin] Add grid shorthand expansion to stylex-valid-shorthands

[abhakat]

Expand grid-area, grid-row, grid-column, and grid-template shorthands into their longhand equivalents with spec-conformant autofix. The grid-area expansion correctly applies the CSS omission rule per-axis, only copying end values from start values for custom-ident groups.

What changed / motivation ?

Want to create the auto-fix to auto-fix future issues.

Linked PR/Issues

Fixes #1476

Additional Context

Added some tests to show/validate behavior

Pre-flight checklist

• I have read the contributing guidelines
  Contribution Guidelines
• Performed a self-review of my code

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
stylex	Skipped		Mar 16, 2026 10:03am

[github-actions]

workflow: benchmarks/perf

Comparison of performance test results, measured in operations per second. Larger is better.
yarn workspace v1.22.22
yarn run v1.22.22
$ node ./compare.js /tmp/tmp.vZ1m0dEH5m /tmp/tmp.GLp8gWRmNM

Results	Base	Patch	Ratio
babel-plugin: stylex.create
· basic create	561	554	0.99	-
· complex create	68	68	1.00
babel-plugin: stylex.createTheme
· basic themes	425	428	1.01	+
· complex themes	35	35	1.00
Done in 0.07s.
Done in 0.29s.

[github-actions]

workflow: benchmarks/size

Comparison of minified (terser) and compressed (brotli) size results, measured in bytes. Smaller is better.
yarn workspace v1.22.22
yarn run v1.22.22
$ node ./compare.js /tmp/tmp.62WWz3SiJT /tmp/tmp.euTnilQJTp

Results	Base	Patch	Ratio
@stylexjs/stylex/lib/cjs/stylex.js
· compressed	1,331	1,331	1.00
· minified	4,209	4,209	1.00
@stylexjs/stylex/lib/cjs/inject.js
· compressed	1,793	1,793	1.00
· minified	4,915	4,915	1.00
benchmarks/size/.build/bundle.js
· compressed	496,650	496,650	1.00
· minified	4,847,840	4,847,840	1.00
benchmarks/size/.build/stylex.css
· compressed	99,653	99,867	1.00	+
· minified	747,850	747,613	1.00	-
Done in 0.09s.
Done in 0.33s.