feat: add eslint-plugin-playwright via oxlint JS plugins (#11136)

## Summary

Add eslint-plugin-playwright as an oxlint JS plugin scoped to
browser_tests/, enforcing Playwright best practices at lint time.

## Changes

- **What**: Configure eslint-plugin-playwright@2.10.1 via oxlint's alpha
`jsPlugins` field (`.oxlintrc.json` override scoped to
`browser_tests/**/*.ts`). 18 recommended rules +
`prefer-native-locators` + `require-to-pass-timeout` at error severity.
All 173 initial violations resolved (config, auto-fix, manual fixes).
`no-force-option` set to off — 28 violations need triage (canvas overlay
workarounds vs unnecessary force) in a dedicated PR.
- **Dependencies**: `eslint-plugin-playwright@^2.10.1` (devDependency,
required by oxlint jsPlugins at runtime)

## Review Focus

- `.oxlintrc.json` override structure — this is the first use of
oxlint's JS plugins alpha feature in this repo
- Manual fixes in spec files: `waitForSelector` → `locator.waitFor`,
deprecated page methods → locator equivalents, `toPass()` timeout
additions
- Compound CSS selectors replaced with `.and()` (Playwright native
locator composition) to avoid `prefer-native-locators` suppressions
- Lint script changes in `package.json` to include `browser_tests/` in
oxlint targets

---------

Co-authored-by: Amp <amp@ampcode.com>
Co-authored-by: GitHub Action <action@github.com>

browser_tests/fixtures/helpers/AppModeHelper.ts

@@ -53,7 +53,7 @@ export class AppModeHelper {
     this.outputPlaceholder = this.page.getByTestId(
       TestIds.builder.outputPlaceholder
     )
-    this.linearWidgets = this.page.locator('[data-testid="linear-widgets"]')
+    this.linearWidgets = this.page.getByTestId('linear-widgets')
     this.imagePickerPopover = this.page
       .getByRole('dialog')
       .filter({ has: this.page.getByRole('button', { name: 'All' }) })