[fnzko]

What does this PR do?

Part of #277.
Depends on #348 (until it merges, only the last 2 commits are new here).

The Agent Plugins format requires every package path to resolve inside the package folder. #348 enforces that for the manifest, the skills folder and each SKILL.md, but a link elsewhere in a skill could still leave the package, and installing a skill follows links wherever they point, so outside content reached every agent's skills folder.

Now a file or folder in a plugin.json package's skill that resolves outside it is left out of the installed copy and reported. The rest of the skill installs, and an unchanged package is not reinstalled. Other plugins keep following links anywhere.

Verified with a unit test of the walk and an integration test syncing a registry package that links out of it.

Take into account:

• Whichever of this PR and feat(agent-plugins): install global plugins as native agent plugins #332 merges second passes the package root to feat(agent-plugins): install global plugins as native agent plugins #332's compiled copy, which still follows such links.
• The warning appears when a skill is installed or updated, once per agent copy, like a broken link's.

Disclosure questions

AI disclosure.

• The AI tool authored large parts of the code

[fnzko]

Folded into #348.