A skill is a capability only when something proves it

Rationale

A skill file makes a procedure exist. Existence is the weakest thing a catalogue can say about an entry, and a catalogue that says only that is a registry whose entries rot: nothing exercises the procedure, nothing points a worker at it, and nobody can tell from the repository whether it still describes what the tools do. Writing tested: true into the file would restate the problem as data — an authored claim that no gate can check.

So the four facts a reader needs are derived where they are true: the tests that name the skill and the runs the evidence ledger recorded for them, the page the site projects, the doctrine and CI gate that hold the file, and the surfaces that reference it (ADR 0076).

Required behaviour

• An active skill is named by at least one test that a runner owns, with the marker majordomus-skill: <id> on a comment line. A marker inside a string is data and binds nothing.
• An active skill is referenced by at least one invocation surface: a workflow, prompt or profile of the layer, a provider template, justfile or .just/, a CI workflow, or a root bootstrap, by majordomus://skill/<id> or by the path of its SKILL.md.
• A test or an invocation that names a skill the repository does not hold is a defect: a binding to nothing reads as proof.
• Status is derived. tested, documented, enforced, used and the standing are answered by skills.status and skills.explain over every surface from one derivation; no skill file, catalogue or site page states them.
• A skill whose concept was studied outside this repository carries only the opaque provenance marker (origin, ledger: import-<date>#<n>, decision); the mapping to its source stays in the local import ledger and is never committed.
• A draft or deprecated skill owes none of this.

Failure behaviour

skills verify exits 10 and names each failure: untested or unused (an orphan), failing (the latest recorded run of a naming test did not pass), contract (the index refused the file), unknown_skill_in_test, unknown_skill_invoked. The same findings reach majordomus doctor through the doctrine majordomus.skill-integrity, and the CI gate skills-proof runs the command on every change to a skill, an invocation surface or the derivation. Evidence that is not current, a missing page and a missing gate are warnings, each with the command that settles it.

Verification

majordomus skills verify
bash test/run.sh 391_skills_are_proven_capabilities
cargo test --manifest-path apps/majordomus-cli/Cargo.toml --test skills