Add effective capability parity contract

[RobLe3]

Summary

• add browser-safe exported effective service capability types, parser, precedence resolver and pure matcher
• pin the exact shared v1 schemas and parity fixture
• preserve complete same-intent variants and portable refusal semantics without changing browser discovery or dispatch

Evidence

• npm test: 45 passed
• npm run typecheck and npm run build passed
• package provenance and dry-run package audit passed

Compatibility

The feature is additive and unused by existing browser consumer/provider, registration, confidentiality and execution paths. Heuristic evidence is accepted only when explicitly labelled and only when stronger evidence is absent. No package was published or deployed.

Closes #11