* add RealtimeTransformResult type for realtime transforms
* add RealtimeProviderConfig pure trait in litellm-core
* add core realtime module
* register realtime module in litellm-core lib
* add OpenAI realtime transform + complete_url parity in providers
* add openai realtime module
* add openai provider module
* register openai provider module in providers lib
* add realtime() fn that invokes OpenAI GA realtime API end to end
* register realtime route module in providers lib
* wire tokio/tokio-tungstenite/futures-util into providers crate
* add tokio, tokio-tungstenite, futures-util to rust workspace deps
* update Cargo.lock for realtime websocket deps
* docs: add litellm-rust provider/route contributor guide
* add typed RealtimeEvent; make RealtimeTransformResult hold typed events
* type RealtimeProviderConfig trait on RealtimeEvent instead of raw strings
* type OpenAI realtime passthrough transforms on RealtimeEvent
* type realtime() fn on RealtimeEvent end to end (parse/serialize at host edge)
* docs: add typed-contracts core rule to core CLAUDE.md
* harden complete_url: default bare host / unknown scheme to wss://
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Co-authored-by: Ishaan Jaffer <ishaanjaffer0324@gmail.com>