loadSkillByName
Look up a registered skill class by name in the global
SkillRegistry, construct an instance, and add it via
addSkill. Returns [false, message] if the name is not
registered, the instantiation fails, or addSkill throws.
Parameters
skillName
Registered skill name (read from the target class’s SKILL_NAME).
config
Optional configuration forwarded to the skill constructor.
Returns
Promise<[boolean, string]> — [true, ''] on success, [false, errorMessage]
otherwise.