Proving claims

• A claim is any checkable assertion: a behavior, a fact about the code, the state of an artifact, or an item in a PR's ## Test plan (or ## How to Verify).
• With no argument, prove the test plan of the current branch's PR, or ask what to prove.
• No claims found means report nothing to prove; never invent a verdict.
• A calling skill passes its claims as a numbered list in a fenced DATA block, with optional context and whether the tree is trusted to execute.
• A caller that does not state trust gets an untrusted tree.

Rules