Authoring a skill for the FGDH catalog

Experimental. This skill has not been verified against a real task since its last change. Verify its output before relying on it.

Preconditions

This skill is pure convention. It needs no toolchain and makes no assumption about where it is running, so it works whether you are authoring inside the catalog repository or drafting a skill somewhere else.

Detect which of the two you are in, because it changes only the verification step:

• Inside the catalog repository — scripts/build_index.py exists at the repository root. The mechanical gate is available; use it, and treat its exit code as the answer.
• Anywhere else — no scripts/build_index.py. The checklist in Verification below is then the whole gate, and the skill is not finished until it has been opened as a pull request against the catalog and passed CI there. Say so explicitly rather than reporting the skill as done.