[FEATURE]: Load skills over MCP #12100

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

Problem: Skill is a proven and effective way to focus a discussion but can be complicated to managed and deploy when numbers are growing.

Solution: MCP server can use resources type skill to discover, expose and update them on the fly. A transparent approach that scale.

Attention: this require HOT LOAD, so OpenCode need to prepare early to land the feature beyond MCP.

Some servers expose them as resources, since the feature landed it means we can define that a resource with skill uri can be hot-loaded in the discussion.

Some discussions
https://github.com/modelcontextprotocol/experimental-ext-skills?tab=readme-ov-file