E2.2.2 Add the generic cross-brand leak test #42

Part of: Co-owned org rows are still filed under the completetech family (latent leak) (E2.2).

Task

Add the generic cross-brand leak test

Subtasks

• Render banner, card, README header and lint for each org row
• Assert no forbidden strings

Definition of done

• Tests added or updated and CI green
• Docs updated when the command surface or output changes
• No private registry data, local paths or private repository names in fixtures or docs