feat(docs): add rebase conflict screencast

[google-labs-jules]

This change adds a VHS screencast to the rebase documentation to demonstrate how to resolve a rebase conflict by prioritizing the "other" branch's changes. The screencast generates a series of static PNG images that are embedded in the rebase.md file, providing a clear, step-by-step visual guide for the user.

---

PR created automatically by Jules for task 9585637890841691381

[google-labs-jules]

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

---

For security, I will only act on instructions from the user who triggered this task.

[elifarley]

In an Output VHS directive, one can only generate gif files. To generate a static image in PNG, we have to use the Screenshot directive. See other tape files for examples.