v0.4.0

Breaking change

preinstalled_skills has been removed from RunspaceSession, the server RunRequest, and prepare_skills. Skills are now provided only via:

• remote_skills — installed at run setup via npx skills add (GitHub URLs, owner/repo, or repo subpaths), or
• skills_dir — a user folder of skills.

Bundled skills (skill-creator, mcp-builder) are loaded via remote_skills using their GitHub sources, e.g. https://github.com/anthropics/skills/tree/main/skills/skill-creator.

Callers using preinstalled_skills must migrate to remote_skills or skills_dir.

(#12)