[Feature] React/Vue/Svelte bindings for the actor-ts client (useActor, useAsk, useTopic)

[pathosDev]

Depends on #435 (typed client).

Rationale

The typed client (#435) gives frontends a protocol-safe transport; framework bindings make it idiomatic: useAsk/useTopic hooks (React), stores (Svelte), composables (Vue) that subscribe to actor topics and drive asks with loading/error state.

Scope

• Subpaths "./client/react", "./client/vue", "./client/svelte" — each with react/vue/svelte as an optional peer dependency (dependency policy: the client core [Feature] actor-ts/client — typed browser/frontend client (ask over WebSocket/HTTP) #435 stays dependency-free; bindings are thin optional layers).
• SSR-safe (no socket during server render; hydrate-on-mount).
• Migrate one chat-example frontend (React) to the bindings as the reference.

const live = useTopic<CounterProtocol>(client, 'changed');
const { value, loading } = useAsk<CounterProtocol>(client, 'counter-1', { kind: 'get' });

Documentation

Client docs chapter section per framework (EN + DE); JSDoc; CHANGELOG; chat-example README update.

Acceptance

• React binding covered by tests (renderHook fixtures); SSR smoke (no window access at import time); chat React frontend runs on the binding.

Non-goals

State-management integrations (Redux/Zustand adapters); optimistic mutations.

Relates

#435; improvement program M7; dependency policy #419.