PixieCore plugin authoring examples

These four complete, offline examples show every public managed-plugin component kind. Each project owns its named TypeScript and YAML entries, compiled JavaScript, implementation under src/, and a plugin-owned test under tests/.

They are equivalent to projects generated by:

pixiecore plugin create ./sample-tool --id=example.sample-tool --kind=tool
pixiecore plugin validate ./sample-tool
pixiecore plugin test ./sample-tool

See the authoring guide for installation, activation, integrity metadata, signing, compatibility, and rollback.