Test262 test harness and initial pass rate #265

Implements issue 3mhn3qbhr3c23

Summary #

• Implement proper try/catch compilation with PushExceptionHandler/PopExceptionHandler bytecode ops (was previously a non-functional stub)
• Add function property support so functions can have arbitrary properties (e.g. assert.sameValue)
• Implement Test262 harness preamble with assert, assert.sameValue, assert.notSameValue, assert.throws, and Test262Error
• Add evaluate_with_preamble and evaluate_with_preamble_limited APIs
• Add VM instruction limit to prevent infinite loops during test execution
• Implement test metadata parsing, feature-based skipping, and grouped pass rate reporting

Initial Pass Rate #

3406 pass, 5523 fail, 14455 skip (38% of 8929 executed)
23384 total language tests

Notable category results: keywords 100%, punctuators 100%, ASI 95%, block-scope 88%, reserved-words 88%, future-reserved-words 87%.

Test plan #

• cargo fmt --all --check
• cargo clippy --workspace -- -D warnings
• cargo test --workspace (all 35 test suites pass)
• cargo test -p we-js --test test262 (harness preamble + language tests)