Delete a skill's directory and it vanishes from the session instead of lingering until restart.
What's wrong with this entry?
Skill discovery can now replace rather than only add, so a skill whose directory you delete is removed from the session instead of lingering until restart.
- In replace mode, previously discovered skills rooted under a scanned directory but no longer present on disk are dropped before the fresh scan is merged in.
- Preconditions are unchanged: discovery is skipped when project settings are disabled or a plugin-only skills policy applies.
tengu_dynamic_skills_changed
Strings lifted out of the shipped bundle, so the claim above can be checked against them.