Describe layer 3 as an object model plus one serializer #43

Parent

#35

What to build

Chapter 30 describes layer 3 the way 0067 and docs/architecture.md already do. Adapters map the Resolved Deployment into the narrow Kubernetes and Vault object model (a model-to-model step), and one serializer turns those objects into bytes (the only model-to-text step).

• A Deliverable carries its path, its object and its adapter. Its content is the serializer's output, not something an adapter writes.
• The executable flag on a Deliverable goes: nothing in the model may be executable (0012).
• CONTEXT.md's entry for "Render" says what the adapters do and what the serializer does, so the vocabulary no longer hides one transformation inside another.

Acceptance criteria

• Chapter 30's Deliverable shape has no content string and no executable flag.
• Chapter 30, 0067, docs/architecture.md and CONTEXT.md describe the same two steps.
• lint:adrs and lint:links pass.

Blocked by

• Rewrite the em-dashes in the specification #26