Support installing complete skill directories with arbitrary nested resources

[ASI2030]

Problem

SkillX can discover and publish nested SKILL.md files and now exposes references/ and scripts/ metadata, but the current consumer command does not install a skill directory. skillx use prints the stored SKILL.md content and optional reference/script metadata to stdout.

Production skills often require arbitrary nested resources beyond those two folders: modules/, assets/, browser adapters, configuration files, templates, tests, and package metadata. Registering such a skill succeeds at the metadata layer, but using it cannot reproduce the runnable source tree.

Public reproduction

Source skill:

https://github.com/ASI2030/Fact-Check-X/tree/main/skills/fact-check-x-complete

The skill has 94 files. Its entry point depends on nested modules and browser runtime assets. The current path:

npx skillx-sh use ASI2030/Fact-Check-X/fact-check-x-complete --raw --include-refs --include-scripts

can expose the instruction content plus reference/script metadata, but cannot deliver the required modules/ and other nested files. The command is therefore useful for discovery and inspection, but it is not a complete installation path for this class of skill.

This follows directly from the current implementation:

• registration fetches the subfolder SKILL.md as the stored skill content;
• resource enrichment only recognizes references/**/*.md and scripts/**;
• skillx use renders content and metadata to stdout and does not write a directory tree.

Expected capability

1. Publish an immutable source commit and a complete file manifest for the selected skill directory.
2. Add a true install command that writes the complete tree while preserving relative paths and safe file modes.
3. Support arbitrary nested resources, not only references/ and scripts/.
4. Verify the installed file count and hashes against the manifest.
5. Distinguish “view/use content” from “install runtime” in the CLI and marketplace UI.
6. Reject path traversal, unsafe symlinks, oversized files, secrets, and unsupported executable modes during packaging/install.

A source-backed archive or commit-pinned Git tree would both work. Until a complete-tree install exists, multi-file skills should be labelled as discovery-only when their runtime cannot be reproduced.