docs: v6.6.3 catch-up - #69

Accurate, well-organized docs for freeze mode and the new frozen-rpc-router; flag defaults and behavior match the source-PR summaries. No correctness blockers, but the port guidance in node-types.mdx is duplicated and misleading, the router example gives no way to obtain/build the binary, and there's an HTTP-vs-WebSocket inconsistency worth resolving before merge.