Declare the Platform Intent metamodel with its cross-document references #41

Parent

#35

What to build

Platform Intent gets what Project Intent got: a wire schema, domain types, a generated class diagram in chapter 14 (the chapter table in chapter 00 says "Diagram: none" today), and the worked Platform document parsed in CI.

Its references into other documents become referential invariants with codes, evaluated wherever both documents are present:

• every engine a Process declares on a volume whose Durability Class derives a backup has an entry in the Platform engines map;
• every Durability Class a volume declares has a Platform durability policy;
• every exposure audience is carried by some tier (E_NO_TIER_FOR_AUDIENCE, existing);
• a tier's proxy names a declared Application.

Parity

TypeScript half of the Task 1 work for Platform Intent (due 2026-09-25). This ticket commits spec/v1/examples/platform/expected/intent.json for the worked Platform document, a refusal fixture with a committed diagnostics.json per referential invariant, and adds Platform Intent's classes to spec/v1/examples/expected/descriptor.json. Cross-document references are references in the descriptor.

The Java counterpart (the Platform document's classes inside the model-driven source metamodel, with Ecore references from a Project into it, the grammar rules for platform.intent.yml, and a Complete OCL invariant per code over the pair of documents) is its own ticket and must match these files.

Acceptance criteria

• The worked Platform document parses.
• A copy with a missing engine entry, a missing durability policy, or an audience no tier carries fails with the rule's code and a JSON Pointer path.
• Chapter 14 carries a generated class diagram, diff-checked in CI.
• The worked Platform document's canonical output equals its committed expected/intent.json.
• Each referential invariant's refusal fixture has a committed diagnostics.json, and the emitted set equals it.

Blocked by

• Declare the Project Intent metamodel once and parse every example with it #38