fix: throw JS exception instead of silent warning for disposed native object calls in debug mode

[NathanWalker]

• Replaces silent Log() warnings with proper isolate->ThrowException() calls when
  invoking methods on disposed native objects in debug mode
• Provides specific, actionable error messages that name the method, class, and selector
• Still avoids crashing the app in debug mode

Context

The change in #294 (42a5328) prevented crashes during HMR (debug mode only) by replacing tns::Assert with
a Log() warning that silently returned v8::Undefined. While this fixed the crash, it
introduced a regression: errors became undetectable from JS, and undefined values could
silently leak into arrays and other data structures.

This fix takes the middle path — a catchable JS exception that:

1. Doesn't crash the app (HMR-safe)
2. Is detectable via try/catch
3. Prevents silent undefined propagation
4. Gives developers a clear message about what went wrong