Harden JavaScript native boundaries - #98

Summary

• preserve the full signed and unsigned 64-bit range across JavaScript values, arrays, and struct fields
• convert public value, array, and struct misuse from native panics or silent coercion into JavaScript errors
• replace delegate and progress TSFN calls with an owning, per-environment implementation that cleans rejected and teardown-drained payloads
• bound callback queues, preserve async context for same-thread delegate dispatch, and guard Worker/environment teardown
• add feature-gated deterministic TSFN lifecycle tests and run them in CI

Testing

• npm run test:tsfn (11 passed)
• npm run build && npm test (38 passed, 2 skipped)
• cargo check -p jswinrt_rs --features test-hooks
• cargo test -p jswinrt_rs --lib
• cargo test -p dynwinrt test_progress_handler_marshals_u64_value