Consolidate Test Suites

Purpose: place each invariant in one owning test layer only.

Definitions:

• Invariant: the rule that must stay true.
• Owning layer: the lowest layer that truly owns and can prove that rule.
• Canonical suite: the normal existing suite for that owning layer.

Default: reuse an existing canonical suite. Do not create a new standalone regression test unless the exception rule below allows it.

Hard Rules