Avoid copying the glob work queue

[OskarEichler]

Problem: Recursive glob traversal used queue replacement, copying every outstanding work item each time a directory was expanded.

Fix: Append children in place with concat, preserving breadth-first traversal and result order while avoiding repeated queue copies.

Verification: The existing directory regression suite passes: 3 runs / 18 assertions. The full suite reaches 433 runs / 1,196 assertions with only the pre-existing Ruby 4 StartTest positional-hash/keyword expectation failure. A 50,000-append synthetic benchmark improved from 0.474823s to 0.002316s.