## Summary
- Fix debug assertion failure in `JSWrappingFunction` when
`expect.extend()` is called with objects containing non-`JSFunction`
callables
- The crash occurred because `jsCast<JSFunction*>` was used, which
asserts the value inherits from `JSFunction`, but callable class
constructors (like `Expect`) inherit from `InternalFunction` instead
## Changes
- Change `JSWrappingFunction` to store `JSObject*` instead of
`JSFunction*`
- Use `jsDynamicCast` instead of `jsCast` in `getWrappedFunction`
- Use `getObject()` instead of `jsCast` in `create()`
## Reproduction
```js
const jest = Bun.jest();
jest.expect.extend(jest);
```
Before fix (debug build):
```
ASSERTION FAILED: !from || from->JSCell::inherits(std::remove_pointer<To>::type::info())
JSCast.h(40) : To JSC::jsCast(From *) [To = JSC::JSFunction *, From = JSC::JSCell]
```
After fix: Properly throws `TypeError: expect.extend: 'jest' is not a
valid matcher`
## Test plan
- [x] Added regression test
`test/regression/issue/fuzzer-ENG-22942.test.ts`
- [x] Existing `expect-extend.test.js` tests pass (27 tests)
- [x] Build succeeds
Fixes ENG-22942
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Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
