feat: MCP (Model Context Protocol) server

- POST /mcp (JSON-RPC 2.0): initialize, ping, tools/list, tools/call; notifications -> 202
- tools: cortiq_route (classify -> routing decision) and cortiq_chat (route -> answer)
- gated by protocols.mcp; admin meta marks it implemented
- docs: README/README.ru protocol tables, highlights and status updated for
  streaming, Anthropic, embeddings, semantic cache and MCP

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -23,6 +23,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/).
   semantically near a previous one (cosine threshold, TTL, ring buffer), skipping the
   model call. Partitioned by routing signature; hit-rate and cost saved are tracked and
   shown on the dashboard; configurable from Settings (`[cache]`).
+- **MCP server** (`POST /mcp`, JSON-RPC 2.0): exposes routing to MCP-native orchestrators
+  via two tools — `cortiq_route` (classify → decision) and `cortiq_chat` (route → answer).
 
 ## [0.1.0] - 2026-06-30