Custom-skill detection heuristic references a field (`skills.json[skills][].slug`) that may not exist

Opus finding

Custom-skill detection heuristic references a field (`skills.json[skills][].slug`) that may not exist

• skills/v4-readiness/SKILL.md:156-158
• skills/v4-readiness/SKILL.md:196-199

Step 4 says the upstream marker is the `install:` line referencing aaronjmars/aeon, but the Methodology block keys on a `slug` field plus an `install` line. The Review table for skills.json (line ~115) cites the schema as `version`, `categories`, `skills[].install` — there's no documented `slug` field. If the executor follows the Methodology literally and skills.json keys entries by `name` rather than `slug`, every upstream skill will be misclassified as custom, inflating the Custom bucket and the notify body. This contradiction will produce wrong verdicts the first time it runs against a real fork.