Update test262 suite to latest commit and fix 3 new failures

[Copilot]

Advances the test262 suite SHA to the latest commit (5c8206929d81b2d3d727ca6aac56c18358c8d790, 2026-03-21) and resolves the 9 newly failing tests across three categories.

Changes

Test262Harness.settings.json

• Bumped SuiteGitSha to latest tc39/test262 HEAD
• Added import-text to ExcludedFeatures — new tests for importing files as raw strings via with { type: 'text' } (not implemented in Jint)

Temporal.Instant.prototype.round — null-prototype options object

When round() receives a string shorthand, the synthetic options object was created with new JsObject (inherits Object.prototype). Per spec, it must use a null-prototype object so inherited properties are not observed:

// Before
roundToObj = new JsObject(_engine);
// After
roundToObj = ObjectInstance.OrdinaryObjectCreate(_engine, null);

AsyncDisposableStack.prototype.disposeAsync — return a Promise

The method was returning the raw disposal result (undefined) instead of a Promise. Per spec, disposeAsync must always return a Promise:

var capability = PromiseConstructor.NewPromiseCapability(_engine, _engine.Realm.Intrinsics.Promise);
try { capability.Resolve.Call(Undefined, stack.Dispose()); }
catch (JavaScriptException e) { capability.Reject.Call(Undefined, e.Error); }
return capability.PromiseInstance;

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• https://api.github.com/repos/tc39/test262/commits/main
  • Triggering command: /usr/bin/curl curl -s REDACTED (http block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

update test262 settings json to point to latest commit in test262 repository, run tests and fix issues until compiles, create a pr with changes

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