[gdpu11]

ElementsMatch(t, [2]int{}, []int{}) currently succeeds even though one collection contains two elements and the other contains none. NotElementsMatch gives the inverse wrong result, and comparing nil with a nonempty collection panics. These incorrect results can hide bugs in tests using zero-filled arrays.

The general Empty assertion intentionally treats a zero-valued array as empty, but collection equality must count its elements. Remove that shortcut from the two collection assertions and let their existing list-diff owner handle nil as a zero-length list. Empty itself and the public API remain unchanged.

Validation with Go 1.26.0 on macOS arm64:

• New public assertion table cases fail on base 87a7b9d57689f6579db2da795ab8deeab29cb724, with wrong zero-array results and a nil-reflection panic.
• Regressions cover zero-filled array/slice equality, differing array lengths, empty collections, and nil versus nonempty collections in both positions.
• go test ./... and go vet ./... pass.
• gofmt and git diff --check are clean.
• Independent autoreview found no actionable regressions.