refactor(engine): remove expect()-based panics from JsRegExp wrapper

[Shivampal157]

While auditing the core engine's error handling, I found that the JsRegExp convenience wrapper relies on .expect() for internal invariants that are not strictly enforced by the type system. These can lead to host process crashes if a regression occurs in the engine.
Locations:
boa/core/engine/src/object/builtins/jsregexp.rs: Around L59–L68 (in JsRegExp::new).
boa/core/engine/src/object/builtins/jsregexp.rs: Boolean accessors (e.g., global, multiline) around L83–L108.
Proposed Fix:
Replace .expect() in JsRegExp::new with proper error propagation returning JsNativeError::internal().
Use ToBoolean semantics or explicit type checks instead of .as_boolean().expect() in accessors.

[Shivampal157]

I've analyzed the panic points in jsregexp.rs and I'm ready to refactor them to use JsNativeError for proper error propagation. This will make the engine more robust against internal regressions. Can I be assigned to this?

[shreyadesai20042009]

Hi! I’m interested in working on this refactor as well.

I’ve been contributing to Boa and would like to help improve error handling in JsRegExp.

If the issue is not yet assigned, I’d be happy to take it up. Otherwise, I can help with review or testing.

[Shivampal157]

Hi @shreyadesai20042009, thanks for reaching out! I've already analyzed the panic points and I'm currently working on a Pull Request for this refactor to improve the engine's stability. I'll be submitting it soon.