Deprecate pasted-text fallback in `useInput` and make `usePaste` the only paste API

[sindresorhus]

Probably not soon, but at some point.

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Summary

useInput currently still receives pasted text when no usePaste listener is active. This is legacy behavior and makes input semantics inconsistent.

Proposal

• Deprecate pasted-text delivery via useInput in the current major.
• In the next major, stop forwarding bracketed paste payloads to useInput.
• Keep usePaste as the dedicated API for paste blobs.

Why

• Clearer API boundaries: key events (useInput) vs paste blobs (usePaste).
• Simpler handlers: no mixed key/paste assumptions in one callback.
• More predictable behavior across terminals.

Migration

If your app relies on pasted text in useInput, switch to usePaste for paste handling and keep useInput for typed key events.

[mehdiraized]

I picked this up in #923.

This PR deprecates the current useInput pasted-text fallback without breaking existing behavior yet:

• useInput still receives bracketed paste when no usePaste handler is active
• Ink now shows a deprecation warning for that legacy fallback
• docs were updated to make usePaste the dedicated paste API and clarify the migration path

If this approach looks good, the next major can remove the fallback entirely and keep paste handling exclusive to usePaste.

[sindresorhus]

Probably not soon, but at some point.

First sentence in the issue.