apr qa: every gate skipped reports "All QA gates passed" and exits 0 #5226

Same class as #2876: a gate that answers empty input with PASS.

gates_pass in crates/apr-cli/src/commands/qa.rs is all(|g| g.passed || g.skipped). If every gate is skipped, it is true. The only lower bound is check_min_executed, and that returns true when --min-executed is unset, which is the CLI default. So apr qa m.gguf with every --skip-* flag prints "All QA gates passed (0 executed, N skipped)" and exits 0 (qa_gguf.rs summary).

No CI path depends on this: the model ladder re-judges skips itself. End users get a PASS that measured nothing.

This is a behaviour change, so it is kept out of the #2876 guard branch. Candidate fix: 0 executed gates is a FAIL by name unless the caller asks for it, plus a RED test row for the all-skipped case.

Refs #2876