Support user-defined generic types for `useSharedState` and `usePicker`

[karandeepsingh7070]

Description

Currently, when using useSharedState and usePicker, the inferred types are limited, and developers need to explicitly specify the generic type even if the shared state is already typed. This adds unnecessary boilerplate for developers and makes the DX less clean.

Example:

const [user, setUser] = useSharedState<User>('user');
// or
const userName = usePicker<User, string>('user', user => user.name);

Ideally, the type should be inferred from the store itself so users do not have to re-specify the type repeatedly.

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Proposal

• Allow useSharedState and usePicker to automatically infer types from the registered shared state key.
• Support optional user-defined generic override if needed, but keep it ergonomic for most use cases.

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Benefits

✅ Reduces boilerplate for consumers
✅ Improves DX and type-safety without redundancy
✅ Makes Overwatch APIs feel more modern and aligned with TypeScript best practices

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Tasks

• Refactor useSharedState to infer type based on the key
• Refactor usePicker to infer state type based on the key
• Update documentation examples to showcase cleaner usage

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