[roadmap] StyleX v1.0.0

Creating a place to centralize our broader plans for 2026, consolidate open ideas and discussions, and taskify progress towards v1.0.0. See also (https://github.com/facebook/stylex/discussions/1355)

## Conveniences

One of the common complaints about StyleX is that it leans verbose certain use cases. These are ideas to address that.

- [x] #1357
- [x] #1359
- [x] https://github.com/facebook/stylex/issues/1395
- [x] #1423

## Features

- [x] #1358
- [ ] #1232
- [ ] #1174
- [x] #1363
- [x] #1365
- [ ] #1366

## Website + docs

Most of the docs need an overhaul, and the examples should be updated to use the unplugin whenever possible, or require a general update (as with NextJS). Doc improvements are especially important to support LLM readiness.

- [x] #732
- [x] #1361
- [x] #1256
- [ ] Documentation improvements:
- [ ] https://github.com/facebook/stylex/issues/1061
- [x] https://github.com/facebook/stylex/issues/1364

## CSS bundling improvements

Improvements and optimizations to CSS bundling and build process

- [ ] https://github.com/facebook/stylex/issues/717
- [ ] CSS normalization (dedupe rules, group at-rules) (nice to have)
- [ ] #1482
- [ ] Baseline CSS resets and overrides

## Dev tools

- [ ] https://github.com/facebook/stylex/pull/1401 (and possibly VS Code extension)
- [ ] ESLint improvements (valid-styles, sort keys, stylelint integration)
- [ ] https://github.com/facebook/stylex/issues/1203
- [x] https://github.com/facebook/stylex/issues/787
- [ ] Library codemods for migration from other frameworks

## React Strict DOM

- [ ] Native polyfills (via RSD)
- [ ] `stylex.when.*` APIs
- [ ] inline styles functions
- [ ] `stylex.include` if we decide to bring it back