Create SourceOS-Linux/sourceos-shell repo and seed initial shell scaffold

[mdheller]

Summary

Create the new primary product/runtime repository SourceOS-Linux/sourceos-shell and seed it with the initial shell scaffold.

This issue tracks the repo-creation gap that is currently blocking product code from being placed in its proper home.

Why

We already established the ecosystem split:

• SourceOS-Linux/sourceos-shell = product/runtime code
• SourceOS-Linux/sourceos-spec = shared machine-readable contracts
• SociOS-Linux/source-os = Linux realization surfaces
• SociOS-Linux/albert = temporary launcher bridge only

Until sourceos-shell exists, there is a risk of UI/runtime code drifting into the wrong repositories.

Initial scaffold to seed

sourceos-shell/
├── apps/
│   └── shell-web/
├── packages/
│   ├── ui/
│   ├── bus/
│   └── schema-bindings/
├── services/
│   ├── router/
│   ├── pdf-secure/
│   ├── docd/
│   ├── annotations-adapter/
│   ├── whyis-adapter/
│   └── memex-adapter/
├── templates/
│   └── shifu/
├── content/
│   ├── draft/
│   ├── imported/
│   ├── derived/
│   └── reports/
├── infra/
│   └── compose/
├── .policy/
└── docs/

MVP scope

Seed the repo with:

• monorepo/workspace config
• shell-web starter
• shared UI package starter
• router/pdf-secure/docd service starters
• compose file
• Makefile
• README describing the contract split and repo responsibilities

Acceptance criteria

• SourceOS-Linux/sourceos-shell repo exists
• initial scaffold is committed on default branch
• README states repo boundary and links to sourceos-spec and source-os
• scaffold includes apps/packages/services/infra/content structure
• shell-web, router, and pdf-secure are at least bootable stubs

Proposed owner

@mdheller