GeezerVison

Summary

This PR clarifies the wording around Proxy invariants while keeping the existing beginner-friendly explanation.

The current invariants note mixes two related concepts:

• the normal meaning of internal-method return values, such as [[Set]] returning true for success and false for failure;
• restrictions that JavaScript actually enforces as invariants on Proxy behavior.

The change keeps the former as recommended trap behavior (should) and distinguishes it from the latter.

It also fixes two related details:

• [[GetPrototypeOf]] only has to return the target's actual prototype when the target is non-extensible (and its result must always be an object or null);
• a falsy set result reports that the write failed. Whether this becomes a TypeError depends on the operation using [[Set]]; the push example in this section is such an operation.

No examples or overall structure are changed.

References

• ECMA-262 §6.1.7.2 — Object Internal Methods and Internal Slots
• ECMA-262 §6.1.7.3 — Invariants of the Essential Internal Methods
• ECMA-262 §10.5 — Proxy Object Internal Methods and Internal Slots
• MDN — handler.set()
• MDN — handler.getPrototypeOf()