bump-core-req

Updates the minimum core version requirement for a fleet plugin in all three canonical places: required_core_version and requires["claude-code-hermit"] in hermit-meta.json, and the dependencies entry in plugin.json. Use this skill whenever the user says "bump core requirement", "raise required_core_version", "make <fleet> require core X.Y.Z", "update min core for <fleet> plugin", or finishes shipping a core feature…