cull-tests: Remove tests that protect nothing

Cull the padding without rewriting the suite

cull-tests asks an agent to name the behaviour each test protects. It keeps tests that fail when real behaviour breaks and marks existence checks, compiler duplicates, vendor mock replays, and UI copy snapshots for deletion.

Install it with the Skills CLI:

npx skills add iannuttall/swipe-skills --skill cull-tests

Use it on one test folder first. The skill shows a keep list and a kill list before it edits, and it does not add replacement tests in the same pass.

Review tests the agent cannot explain

The rule is useful, but it still depends on the agent understanding the product contract. A strange test may protect a bug that is not obvious from its name. The skill tells the agent to mark tests it does not understand instead of deleting them. Check that list before accepting the change.