feat(ai): Live API

[daymxn]

Adds support for the Live API through a new LiveSession struct, which is facilitated through a new liveModel method on FirebaseAI. This includes support for the realtime api, as well as the incremental api.

This PR also adds support for the id field in FunctionCallPart.

Fixes #15147

[google-oss-bot]

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⚠️	New public headers were added, did you remember to add them to the umbrella header?

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[ncooke3]

Please audit public API and change mutable stored properties to immutable lets if possible.

[ncooke3]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces support for the Live API, a significant feature enabling real-time, bidirectional communication with the model. The changes are extensive, adding new public-facing classes like LiveGenerativeModel and LiveSession, along with a robust internal infrastructure to handle WebSocket communication, including a LiveSessionService actor and numerous data models for client/server messages.

Overall, the implementation is of very high quality. The separation of concerns is excellent, with clear distinctions between public API, internal services, and low-level networking. The use of modern Swift concurrency features like actors and async streams is well-executed. Error handling is also very thorough, with specific, descriptive error types for the new Live API.

I've identified one high-severity issue related to a hardcoded URL that would prevent testing against non-production environments, and a medium-severity issue regarding the WebSocket delegate setup. My feedback is focused on improving the robustness and correctness of the new networking layer.

[ncooke3]

Great work! Please do a round of testing before merging.