fix(core): contextualize runtime function loader failures

[huytdps13400]

Summary

• wrap thrown runtime-function loader errors as RuntimeFunctionLoadError
• include the function id, actual runtime name, and original cause message before runner serialization
• preserve the original error as a non-enumerable cause locally
• reject non-function loader results before caching them
• explain likely module-initialization or missing native-package failures
• preserve successful loading, caching, and runtime-function invocation behavior

The registered loader is wrapped before it is handed to the JSI registry, while the JS fallback validates before updating its runtime-local cache. Function-body errors remain outside the loader wrapper and keep their existing behavior.

Regression coverage

The new callable-module boundary test covers:

• a loader that throws
• loaders that resolve to undefined or an object
• caller-visible serialized function/runtime context
• local Error.cause
• retry after an invalid result, proving the invalid value was not cached

RED before the implementation: 4/4 regression tests failed with the existing plain Error/TypeError behavior. A separate mutation check removed the cause attachment and failed specifically on the missing-cause assertion.

Verification

Passed locally:

• frozen dependency installation
• focused regression Jest: 4/4
• runnable plain-JS/regression suites: 3 suites, 10/10 tests
• packages/core TypeScript/plugin build
• packages/state TypeScript build
• example tsc --noEmit
• changed-test ESLint
• changed-test Prettier check
• git diff --check

Repository-wide baseline limitations:

• full plain Jest still fails in untouched App.test.tsx because the native NitroModules TurboModule is unavailable outside a built app; the other three suites pass
• full example lint still reports existing errors in untouched legacy tests; the new test lints cleanly
• the real Hermes/JSI path was simulated through the existing JSI globals and callable-module boundary; no device build was required for this JS-boundary fix

Supersedes #44, which GitHub closed automatically when its head branch was renamed.

Fixes #43

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