Repair FileSystemDirectoryHandle.removeEntry WebIDL validation #849

Problem

The exact Linux full-V8 package failed the bounded validation matrix for FileSystemDirectoryHandle.removeEntry(name, options), even though the implementation validates names and dictionary arguments before publishing a host request.

Investigation showed that the six calls correctly reject with TypeError; the gate evaluated the returned async IIFE as a binary interop value before its promise settled, so it observed the promise object as {} rather than the eventual joined exception sequence.

Fix scope

• execute the validation matrix asynchronously into an explicit observable result;
• wait for the settled result with the existing bounded evaluation helper;
• report the actual observed exception sequence on failure;
• assert that rejected calls publish no native removal request.

Acceptance

The focused remove-only full-V8 gate observes six TypeError results, confirms no host request for invalid calls, and retains valid removal success plus DOMException status mapping.

Implementation

Implemented on fix/file-system-remove-validation-849 in commit 06cc4d71.