Add link preview cards to the new-tweet composer

[AlexMnrs]

Feature request

Add a link preview card to the new-tweet composer when a user pastes or types a URL.

Motivation

At the moment, the composer displays the URL as text only. This makes it difficult to know how the link will appear after publishing and is a noticeable difference from the regular X experience.

OldTwitter already renders link cards on published tweets, including summary and summary_large_image cards with a thumbnail, title, description, and destination URL. However, the new-tweet composer does not currently show a preview while the tweet is being written.

Proposed scope

• Detect a URL in the new-tweet composer.
• Show a preview card with the available domain, title, description, and thumbnail.
• Update or remove the preview when the URL changes or is removed.
• Reuse the existing card rendering where practical.
• When publishing, use the card mechanism supported by X if the required metadata or card URI is available.

The implementation should not require arbitrary client-side fetching of third-party pages if that would introduce CORS, privacy, or security problems. It would be useful to first confirm which response/API path X currently uses to generate or associate a card for a URL.

Current implementation notes

• The composer is implemented in layouts/home/script.js.
• Existing published-tweet card rendering is handled by generateCard in scripts/helpers.js.
• scripts/apis.js already handles card_uri, while the composer currently uses that path for polls rather than ordinary URL previews.

This request is intentionally limited to link previews in the new-tweet composer; video previews, media-tab changes, and other composer improvements should be tracked separately.