Add QR code to remote control link toast

[zachlloyd]

Description

Adds a QR code below the "Remote control link copied." toast. The QR image is generated from the copied remote-control link, inserted into the raw asset cache, and rendered at the shared toast width.

Linked Issue

• The linked issue is labeled ready-to-spec or ready-to-implement.
• Where appropriate, screenshots or a short video of the implementation are included below (especially for user-visible or UI changes).

Testing

• cargo check -p warp --lib

• I have manually tested my changes locally with ./script/run

Screenshots / Videos

Agent Mode

• Warp Agent Mode - This PR was created via Warp's AI Agent Mode

CHANGELOG-IMPROVEMENT: Show a QR code for copied remote control links.

Slack Thread

  

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