Built-in skills silently introduced by updates conflict with existing custom skills, with no way to disable them

Custom skills that were working under a given name (e.g. /review) break silently when a Claude Code update introduces a built-in with the same name. The built-in takes precedence, the custom skill is effectively displaced, and there is no mechanism to disable or override the built-in.

Impact:

• Existing workflows break without warning at the point of use — there is no notification that an update introduced a conflicting built-in
• Users are forced to rename their custom skills (and update all references) to avoid current and potential future collisions
• There is no way to know in advance which names are "safe" to use

Requested changes:

1. A disabledCommands (or disabledSkills) array in settings.json so users can opt out of specific built-ins
2. At minimum, a warning or notification when an auto-update introduces a built-in that conflicts with an existing custom skill
3. (Ideal) Custom skills should be able to override built-ins of the same name — the user's explicit configuration should win

Workaround currently required: Adopt a namespace prefix (e.g. eg-) across all custom skills to avoid collisions with present and future built-ins.