[Possible Roadmap] Add a first-class authoring/build/pack/install pipeline for external modules

[MehmetSecgin]

Summary

Move external modules toward a complete dispatch-native lifecycle: init, build, validate, pack, and install.

Why

If external modules are central to the product story, their creation and distribution should not feel like sidecar glue.

Desired direction

Potential long-term command surface:

• dispatch module init
• dispatch module build
• dispatch module validate
• dispatch module pack
• dispatch module install

Principles

• author in TS
• compile/bundle ahead of time
• load built JS at runtime
• validate the built module contract
• make installation and sharing consistent across teams

Open questions

• Should dispatch own the build step directly, or just define the contract initially?
• Should module packaging be tarball-based, directory-based, or both?
• How much bundling should be required for reliable installed modules?

Related: #20