Refresh global, external, and HTTP skill sources without restart

[kitlangton]

Parent

Related to #8751.

What to build

Extend V2 skill-content refresh beyond skill files inside watched git project Locations.

Project .opencode/skills content currently invalidates through the Location filesystem watcher. Global compatibility roots, explicitly configured external directories, non-git Locations, and already cached HTTP catalogs do not have a continuous invalidation path. Replaying an unchanged source registration also does not clear its cached content.

Acceptance criteria

• Global OpenCode, .claude, and .agents skill edits refresh in loaded Locations.
• Explicit external skill directories refresh without requiring an unrelated config edit or restart.
• HTTP catalogs have a defined refresh trigger and observe a changed version while OpenCode remains running.
• Skill removal clears model-facing guidance and slash visibility on the next safe boundary.
• Tests document and cover project, global, external, non-git, and HTTP source behavior.

Blocked by

None - can start immediately.

[Shalin-Shah-2002]

Hi! I'd like to work on this issue if it's available.
I'll investigate the current skill refresh flow and submit a PR.