test: add custom toMatchObject matcher for @std/expect compatibility

test: add custom toMatchObject matcher for @std/expect compatibility

Implement custom Vitest matcher that replicates @std/expect's toMatchObject
semantics for arrays. The matcher handles sparse array subset matching where
only defined indices are compared, matching the behavior of @std/expect's
spread-based algorithm in _equal.ts.

This fixes 8 failing tests in queue test files that use toMatchObject with
sparse arrays created via new Array(capacity).