fix(skill): show active skill live during turn

[cniska]

Summary

• surface an activated skill on the status line live (mid-turn) instead of only after the turn resolves
• add a typed skill-activated stream event carrying the skill; the server emits it on activation and the client applies it to the live session, which the post-turn reconcile then confirms
• make lifecycle.summary.active_skills report the end-of-turn session set, so a skill activated mid-turn shows in that turn's trace instead of a turn late