docs(persist): add U=T default to persist middleware signature

[TheSeydiCharyyev]

The persist middleware signature in the reference docs is missing the U = T default that's present in src/middleware/persist.ts:

// src/middleware/persist.ts
type Persist = <
  T,
  Mps extends [StoreMutatorIdentifier, unknown][] = [],
  Mcs extends [StoreMutatorIdentifier, unknown][] = [],
  U = T,    // ← default
>(
  initializer: StateCreator<T, [...Mps, ['zustand/persist', unknown]], Mcs>,
  options: PersistOptions<T, U>,
) => StateCreator<T, Mps, [['zustand/persist', U], ...Mcs]>

Without the default, callers must always specify both generics. With U = T, the default case (where the persisted shape matches the full state — i.e. no partialize) lets users write persist<MyStore>(...) instead of persist<MyStore, MyStore>(...).

Diff

- persist<T, U>(stateCreatorFn: StateCreator<T, [], []>, persistOptions: PersistOptions<T, U>): StateCreator<T, [['zustand/persist', U]], []>
+ persist<T, U = T>(stateCreatorFn: StateCreator<T, [], []>, persistOptions: PersistOptions<T, U>): StateCreator<T, [['zustand/persist', U]], []>

Single change: <T, U> → <T, U = T>.

Continuing the reference-docs alignment pass — see #3487, #3489, #3491, #3492.

Docs-only — no changeset needed.

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Project	Deployment	Actions	Updated (UTC)
zustand-demo	Ready	Preview, Comment	May 10, 2026 4:36am

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