Make callable module lookup prototype-safe

[OskarEichler]

Summary:

The legacy bridge stores lazy callable modules in an ordinary object. Unregistered names such as constructor therefore resolve through Object.prototype, while registering __proto__ mutates the registry prototype. Store the internal string-keyed module map without a prototype and add exact lookup/registration regressions.

Fixes #58198.

Changelog:

[GENERAL] [FIXED] - Prevent inherited Object properties from resolving as legacy callable modules.

Test Plan:

• Exact Fantom baseline: 1 failed / 13 passed (constructor returned an inherited object).
• Fixed Hermes Fantom: 14/14 passed, including __proto__ registration.
• Fresh yarn flow-check: 0 errors.
• Targeted ESLint, Prettier, and git diff --check passed.

The one-time local Fantom native build required -Wno-error=deprecated-literal-operator for a vendored nlohmann header under the installed Xcode Clang; the test execution itself is green. No UI change; screenshots are not applicable.