## Summary:

Three Babel plugins added to `@react-native/babel-preset` that work
around runtime codegen bugs in the bundled Hermes V1 (250829098.0.13,
branch cut 2025-08-29) by rewriting source patterns before they reach
the engine. Each plugin papers over a different bug that is fixed on
Hermes `static_h` but has not been backported to the V1 stable branch
(verified absent through the .0.15 stable tip; the only in-flight graft,
facebook/hermes#2030, is still open).

- `fix-hermes-v1-async-arrow-non-simple-params`:
  facebook/hermes#1761 (fixed in static_h by 68bfb3a48b31, 2025-09-11).
  Async arrow functions with destructured, defaulted, or rest parameters
  silently resolve `await` with `undefined` while the function body
  continues executing in the background. The plugin rewrites the params
  to a simple identifier with inline destructuring so Hermes never sees
  the buggy shape. Gated on `isHermesProfile && preserveAsync` since
  `plugin-transform-async-to-generator` rewrites the pattern away when
  `preserveAsync` is false.

- `fix-hermes-v1-class-in-finally`:
  Fixed in static_h by 1e94fbe0ebb4 (2026-02-12). Class declarations
  inside a `finally` block trip Hermes V1's variable caching path. The
  plugin wraps them in an IIFE so the class lives in its own scope, and
  preserves the inferred name of a class expression bound to a plain
  identifier.

- `fix-hermes-v1-super-in-object-accessor`:
  Fixed in static_h by 18a963465944 (2025-11-04). Object-literal getters
  and setters using `super.x` trip the `genFunctionExpression` home
  object path, which segfaults hermesc at compile time. The plugin marks
  the accessor as computed with a string key, covering identifier,
  string, and numeric keys.

All three gate on `isHermesProfile` and bail out fast on the common
case. The plugins are a direct port of work by @kitten (Phil Pluckthun,
Expo team) in `babel-preset-expo` (expo/expo#45601, MIT licensed). All
plugin design and implementation credit belongs to him. This PR carries
his work over to `@react-native/babel-preset` so bare React Native
consumers benefit from the same fix.

## Changelog:

[GENERAL] [FIXED] - Work around three Hermes V1 source-level codegen bugs in `@react-native/babel-preset` (async-arrow non-simple params, class-in-finally, super-in-object-accessor)

## Test Plan:

- 21 inline-snapshot test cases across three new test files verify the transformed output, the fast-bail behavior on irrelevant patterns, and the numeric-key and class-name edge cases.
- `yarn jest packages/react-native-babel-preset` clean (76 tests, 27 snapshots).
- Full repo `yarn test` clean (278 suites, 5692 tests passed, 1857 snapshots).
- `yarn lint`, `yarn format-check`, `yarn flow-check`, `yarn test-typescript`, `yarn featureflags --verify-unchanged`, `yarn build-types --validate` all clean.
- Existing `transform-snapshot-test` passes byte-identical: the kitchen-sink fixture has none of the buggy patterns so the new plugins do not change its output for any profile.
- Compiled the bug patterns through the bundled compiler (hermes-compiler 250829098.0.14): `get x() { return super.x }` and `get 0() { return super.x }` both segfault hermesc, while the transformed computed-key output compiles clean.
- Device repro at ramonclaudio/hermes-1761-repro: 55/55 PASS on iPhone 17 Pro / iOS 26.5 in Debug and Release.

## Caveats:

`fix-hermes-v1-class-in-finally` rewrites block-scoped `class`
declarations inside `finally` blocks to function-scoped `var`
initializers, matching the babel-preset-expo source. Observable only
when code in the same `finally` references the class before its
declaration or relies on its block scoping (rare). The same plugin shape
has shipped in `babel-preset-expo` and Expo SDK 56 without reported
regressions, but flagging in case Meta's internal test fleet surfaces an
edge case the OSS suite does not catch.

## References:

- facebook/hermes#1761 (root-cause issue, fixed in static_h)
- facebook/hermes#2030 (in-flight graft of the async-arrow fix onto the V1 stable branch, still open)
- expo/expo#45601 (source of the ported plugins, by @kitten)
- expo/expo#45592 (user-facing bug report on SDK 56 preview)

Co-authored-by: Phil Pluckthun <phil@kitten.sh>