Packager/publisher declare package content (assets vs code)

[diegohb]

What to build

The packager and publisher derive a content declaration from the package's asset inventory and write it into the generated package's package.json:

• "content": "assets" — the package ships only skills and/or commands
• "content": "code" — the package ships anything else (agents, tools, hooks, other plugin integrations); code-backed packages may also ship skills/commands

The declaration is what installers use to pick the deployment plan (ADR-0008). The package templates carry the field, and the packager's inventory step is its source of truth.

Acceptance criteria

• Packaging a skills/commands-only project produces a package declaring assets
• Packaging a project with any agent, tool, or plugin content produces code
• The generated package templates include the declaration field
• The publisher's post-publish verification covers the declaration's presence

Blocked by

None (can start immediately).