No bindings for Firebase AI Logic

ReactFire ships a provider and hook set for nine Firebase products and none for Firebase AI Logic (`@firebase/ai`). An app that uses it initializes it by hand, outside the `FirebaseAppProvider` tree the rest of the app runs through.

`src/sdk.tsx` declares `AppCheckProvider`, `AuthProvider`, `AnalyticsProvider`, `DatabaseProvider`, `FirestoreProvider`, `FunctionsProvider`, `PerformanceProvider`, `StorageProvider` and `RemoteConfigProvider`, each with a matching `useX` and `useInitX`. A search of `src/` for `getAI`, `firebase/ai` or `@firebase/ai` returns nothing (control: `FirebaseAppProvider` appears in two files, so the search can return hits).

### Why this surface wants hooks more than most

AI Logic is stream and session shaped, which is exactly the async state a hook is good at and the raw SDK leaves to the caller:

- **`generateContentStream`** returns an async iterable plus an aggregated response promise. Consuming it in React means accumulating tokens into state, and cancelling the in-flight request when the component unmounts. Neither has an obvious idiom today.
- **`ChatSession.sendMessage` / `sendMessageStream`** hold conversation history that is naturally component state, currently kept by hand alongside the session object.
- **One-shot `generateContent`** is the trivial case and falls out of the same binding.

### What it looks like in practice

Both demo apps in this repository hit it. In the ReactFire recipe demo (#798) the AI page is byte-identical to the plain SDK version, because there is no binding to differ: the page calls the SDK directly, taking the `FirebaseApp` from `useFirebaseApp()`. That is a fair outcome rather than a bug, but it is the only page in the comparison where ReactFire has nothing to offer, and a reader notices that the app reaches around the provider tree for one product and through it for the others.

### Scope

Out of scope for now: `LiveSession` and `startAudioConversation`, which are Public Preview. The connect and teardown lifecycle there is a strong hook candidate and worth revisiting once the API is stable, but filing against a preview surface is premature.

### Notes

No existing issue covers this: searches for "AI Logic", "gemini", "vertex" and "genai" in issue titles return nothing across open and closed, with a control search returning results.

Filed at @jhuleatt's request from the 2026-08-24 sync: file AI Logic features that ReactFire does not support as issues so they can be reviewed and prioritized.

Start with the provider, hook, and initializer declarations in src/sdk.tsx, then compare the ReactFire recipe demo from #798 with its plain Firebase AI Logic usage. Review the existing FirebaseAppProvider references and the @firebase/ai surface described in the issue. Done means a reviewed binding for the stable generateContent, generateContentStream, and ChatSession cases, while leaving LiveSession and startAudioConversation out of scope.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.