fix: preserve caret position in controlled custom fields

[rinormhi]

Closes #1642

Description

This PR fixes a bug in Puck where controlled custom input fields would move the caret to the end on every keystroke while editing existing text.

The root cause was that custom fields read from the local field store, but their value was only reflected back after the async resolveComponentData -> replace roundtrip completed. For controlled inputs, that delayed sync was enough to break normal browser caret preservation.

This change keeps the existing update flow intact, but synchronizes the local field store immediately for custom and override-backed field types so controlled inputs can be edited in place as expected.

Changes made

• Updated AutoField to synchronously mirror changes for custom field types into the local field store before forwarding onChange.
• Applied the same local sync behavior to override-backed field types, since they use the same value path.
• Added a regression test covering controlled custom field updates.

How to test

• Create a custom field that renders a controlled <input>:

const MyTextField = ({ id, value, onChange }) => {
  return (
    <input
      id={id}
      value={value ?? ""}
      onChange={(e) => onChange(e.target.value)}
    />
  );
};

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Project	Deployment	Actions	Updated (UTC)
puck-demo	Ready	Preview, Comment	May 19, 2026 2:45pm