010 T3: Terminal rule: lane fails any `.cs` under a `tests/` dir; drop dual-layout acceptance nf-yrg7 ← Beads

Twinned from https://github.com/cfsh/ninefold/issues/1003 by tools/beads/import_github.py's reconcile pass.

From 010-co-located-tests-and-probes.md's task table (design 010). - Real dependency: T2 - Note: closes the placement loophole — wiring checks alone would let a new correctly-wired tests/ dir pass (B7)