feat(protocol): add OMP operation capability contract

[iarbpairs]

What this changes

I added a shared, bounded operation-capability contract so Flutter and the official OMP runtime adapter can proceed in parallel without inventing separate capability models.

The catalog can now expose stable operationId values with four execution classes: typed, headless, terminal-only, and unavailable. Unsupported operations carry structured disabled reasons, and contradictory states are rejected at the wire boundary.

I added a language-neutral fixture covering an ordinary prompt, verified headless /compact, terminal-only /plan, unavailable goal creation, and explicit terminal_only / capability_unavailable response examples. Flutter now decodes and preserves this contract through catalog frames and catalog.get results.

This PR deliberately does not implement live runtime discovery or dispatch enforcement. Those backend changes will follow from main in a separate runtime-adapter branch while Flutter consumes this contract and fixture.

Checklist

• bun test packages/host-wire/test/app-wire.test.ts passes (42 tests)
• bun test packages/host-service/test/operations.test.ts passes (12 tests)
• bun run --cwd packages/host-wire typecheck passes
• flutter test test/protocol/wire_conformance_test.dart passes (40 tests)
• Focused flutter analyze reports no issues
• LSP diagnostics report no issues for the changed TypeScript and Dart sources
• Any pasted logs or screenshots are redacted: no secrets, tokens, pairing codes, or private paths
• No third-party source was ported in this change