Improve native createTheme token normalization

[yaminyassin]

Replace regex in native createTheme token normalization

Summary

Native css.createTheme no longer uses a regex to strip var(-- and ) from tokens returned by css.defineVars. The code now checks for the generated prefix/suffix and slices the token name directly.

This relies on the existing createTheme contract: the first argument is the return value of defineVars. Native defineVars emits tokens as var(--${name}).

Test Plan

• npm i
• npm run flow
• npm test
• npm run perf --workspace benchmarks
• npm run size --workspace benchmarks

[github-actions]

workflow: benchmarks/perf (native)

Comparison of performance test results, measured in operations per second. Larger is better.

Results	Base	Patch	Ratio
css.create
· small	1,124,845	1,126,457	1.00	+
· small with units	493,254	493,675	1.00	+
· small with variables	659,923	680,878	1.03	+
· several small	348,172	350,466	1.01	+
· large	198,849	200,280	1.01	+
· large with polyfills	144,989	148,144	1.02	+
· complex	101,282	101,824	1.01	+
· unsupported	209,105	210,971	1.01	+
css.createTheme
· simple theme	228,932	564,245	2.46	!!
· polyfill theme	218,567	527,360	2.41	!!

[github-actions]

workflow: benchmarks/size

Comparison of minified (terser) and compressed (brotli) size results, measured in bytes. Smaller is better.

Results	Base	Patch	Ratio
react-strict-dom/dist/web/index.js
· compressed	3,251	3,251	1.00
· minified	10,375	10,375	1.00
react-strict-dom/dist/web/runtime.js
· compressed	1,645	1,645	1.00
· minified	4,131	4,131	1.00
react-strict-dom/dist/native/index.js
· compressed	16,638	16,636	1.00	-
· minified	64,632	64,653	1.00	+
react-strict-animated/dist/web/index.js
· compressed	6,861	6,861	1.00
· minified	23,486	23,486	1.00
react-strict-animated/dist/native/index.js
· compressed	797	797	1.00
· minified	2,518	2,518	1.00