[FEAT] TestHarness :

- Protocol-level test harness: MockBridge (queue + legacy + registry protocols, ephemeral ports) and McpTestClient (stdio JSON-RPC with stdout-purity tracking)
- Gates: tools/list surface shape + 120KB ceiling, queue round-trip with X-Agent-Id, legacy sync fallback, multi-instance selection gate, 4MB hard-limit guard, logical-failure surfacing
- Spec-ahead TODO gates (flip as waves land): serverInfo.version = package.json, 30KB tools/list diet, strict property schemas, MCP isError flag
- Unit tests pin the two-tier surface (68 core + 254 advanced) and the {name, description, inputSchema, handler} tool contract
- Wire npm test + npm run test:stress; GitHub Actions test workflow (ubuntu+windows, node 20/22)