fix(form-core): prevent double re-render when no async validators

[tt-a1i]

Summary

• Fix fields re-rendering twice on each keystroke when there are no async validators
• Add test case to verify isValidating doesn't toggle unnecessarily

Problem

As reported in #1130, fields were re-rendering twice on each keystroke because isValidating was being set to true then immediately false in validateAsync, even when there were no async validators to run.

Root Cause

In FieldApi.validateAsync:

// Before: Always toggled isValidating regardless of validators
if (!this.state.meta.isValidating) {
  this.setMeta((prev) => ({ ...prev, isValidating: true }))  // Render 1
}
// ... later ...
this.setMeta((prev) => ({ ...prev, isValidating: false }))   // Render 2

Solution

Check if there are actual async validators before toggling isValidating:

const hasAsyncValidators =
  validates.some((v) => v.validate) ||
  linkedFieldValidates.some((v) => v.validate)

if (hasAsyncValidators) {
  // Only toggle isValidating if we have validators to run
}

Test Plan

• Added test case: should not toggle isValidating when there are no async validators
• All existing tests pass (404 tests in form-core, 78 tests in react-form)

Fixes #1130

[changeset-bot]

🦋 Changeset detected

Latest commit: 89c5741

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 13 packages

Name	Type
@tanstack/form-core	Patch
@tanstack/angular-form	Patch
@tanstack/form-devtools	Patch
@tanstack/lit-form	Patch
@tanstack/react-form	Patch
@tanstack/solid-form	Patch
@tanstack/svelte-form	Patch
@tanstack/vue-form	Patch
@tanstack/react-form-devtools	Patch
@tanstack/solid-form-devtools	Patch
@tanstack/react-form-nextjs	Patch
@tanstack/react-form-remix	Patch
@tanstack/react-form-start	Patch

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