fix: Animation fixes to reads

[mhambre]

No description provided.

[Copilot]

Pull request overview

This PR updates the animation tooling and assets used to generate README-friendly visuals for SparseIO, with small cleanups to the general-read manim scene and improved setup/runtime checks for rendering.

Changes:

• Update animation setup docs to install dependencies from requirements.txt instead of a hardcoded manim pin.
• Simplify the general-read scene by removing unused imports/constants/helpers.
• Add an ffmpeg presence check and ensure requirements are installed on each render run; add alt text for the README animation.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
scripts/animations/README.md	Switch setup instructions to pip install -r requirements.txt.
scripts/animations/general-read/scene.py	Remove unused manim import and prefetch/stream helper code.
scripts/animations/common.sh	Add ffmpeg check and always install requirements when rendering.
README.md	Add descriptive alt text to the embedded animation image.

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