Allow importing a skill from a GitHub URL

[thesobercoder]

Importing currently means having the skill on disk already: bun scripts/import.ts /path/to/skills (README.md:225) walks local directories. There is no way to import from a URL, and no import route in the HTTP API or UI.

That is an awkward gap for a self-hosted library, because the natural way to share a skill is to link a repo or a folder in one. Pasting a GitHub URL is the obvious entry point.

What it could accept

• A repo: https://github.com/owner/repo
• A folder inside one: https://github.com/owner/repo/tree/main/skills/my-skill
• Ideally a single file: https://github.com/owner/repo/blob/main/my-skill/SKILL.md

Things worth deciding up front

• Private repos. A public-only fetch needs no credentials. Private support means asking for a token and storing it encrypted — the same scheme already used for the Jev key and Executor credentials (src/server/secret-storage.ts).
• SKILL.md at the root. The existing import requires SKILL.md in each skill directory (scripts/import.ts:42), so a fetched folder should be validated the same way rather than inventing a second rule.
• Frontmatter name must match the id. inspectSkillPackage enforces frontmatter.name === id (src/skill-manifest.ts:190). A URL import needs a clear policy on which one wins, or a clear error.
• Integrity and limits. Portability limits are 512 files / 16 MiB (src/skill-manifest.ts:106-109). A fetch should enforce those before writing, not after.
• No code execution. Skillbox never runs uploaded code, and a URL import should keep that property: fetch bytes, verify, publish. No installs, no build steps.
• Path safety. Reuse the existing safePath / validPath checks so a crafted archive or repo cannot traverse out of the skill directory.
• Secret scanning. scripts/import.ts:105-114 already quarantines recognizable secret patterns as a heuristic. A URL import should run the same check — it matters more here, since the source is arbitrary and remote.
• Pinning. A URL import resolves to a moving branch. Recording the resolved commit SHA with the revision would make the import reproducible.

Why this is worth doing

It turns the library from "skills I already have locally" into "skills I can pull from anywhere," which is the main reason to run a shared library at all. It also pairs well with the existing export format (skillbox-export/v1), so a repo could be a published library that others import directly.

Happy to prototype this if it would help.