fix: avoid post-Chrome-79 ES builtins that white-screen on old WebView
The multisig group-profile e2e white-screened on CI's api-31 emulator: its
WebView is Chrome 91, but `Array/String.prototype.at` (ES2022) and
`Object.hasOwn` (ES2022) ship untranspiled (ts-loader, target es2022, no
core-js). On the group-profile-setup screen `connection.label.at(0)` threw
`TypeError` mid-render, React unmounted the tree with no boundary, and #root
went blank — the real cause behind the "setup-members-segment never displays"
timeout (keria had already resolved the member fine).
This violates the app's own .browserslistrc floor (Chrome >=79), which until
now nothing enforced for JS APIs.
- Replace all 11 `.at()` with bracket indexing and the 3 `Object.hasOwn`
with `Object.prototype.hasOwnProperty.call` (identical semantics, ES2015-safe).
- Add eslint-plugin-es-x wired to fail lint on runtime builtins newer than the
browserslist floor (at/hasOwn/replaceAll/promise.any/findLast/toSorted/...),
scoped to shipped app source (tests run in modern jsdom). compat plugin was
evaluated but misses prototype-method builtins, so es-x is used instead.
Co-Authored-By: Claude Opus 4.8 <[email protected]>
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