Replace the legacy long-goal skill contract with command-scoped goal tools and runtime guidance. Keep goal state durable across continuations while restricting create and replace mutations to explicit user /goal turns.
- Register /skill in BUILTIN_COMMAND_SPECS with wrench icon - Add cmd_skill handler that lists skill names and descriptions - Disabled skills are excluded from the output - Add 6 tests covering empty list, names/descriptions, disabled filtering, fallback description, markdown output, and router registration