Add Prompt SDK conformance suite and reference prompts (#71)

[andrewperis]

Summary

• Add reusable adapter boundary conformance tests, exercised by MockTextAdapter and an independent fake.
• Add synthetic text, structured-output and context-package reference flows with deterministic reviewed golden fixtures.
• Exercise expired context, schema-invalid structured output, provenance validation and non-public redaction end to end.
• Document the existing full contract coverage map, adapter test integration and golden review policy.
• Add read-only GitHub Actions CI on Node 22 and 24 with immutable action pins and no provider secrets or paid calls.

Verification

• npm test: 100 local tests pass.
• git diff --check passes.
• No new dependencies or production contract changes.
• CI matrix results must pass before merge.

Scope

Reference artifact identifiers and context are synthetic. Image/multimodal execution is not supported by this v1 contract. Real-provider transport mapping tests and immutable publication under Studio #72 remain separate.

Closes DefinitelySecureStudio/studio#71

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-11T14:25:06.652756Z	0ed2792	Draft marked ready

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