Add a non-AW command package fixture to prove generator portability

[rickardvh]

Origin: rickardvh/agentic-workspace#1253

The AW extraction seam review found that command-generation is now consumed as an external dependency, but all inspected generated packages are still AW-family packages. The generator needs at least one non-AW/minimal command package fixture so portability is proven outside AW-shaped operation ids, resource roots, package roles, and runtime support.

Acceptance:

• Add a minimal non-AW command package fixture in this repo.
• Exercise parser/help generation, primitive registry extension, and at least one target renderer.
• The fixture must not depend on AW operation ids, resource roots, package names, or runtime support files.
• Include a conformance/check path that would fail if AW-specific assumptions are required.

This is a generator-side follow-up from the AW #1253 seam review.