🎨 Palette: Add aria-labels to icon-only buttons

[threehymns]

💡 What: Added missing aria-label attributes to multiple icon-only buttons across the GraphTab and CodeBlock components.
🎯 Why: To improve accessibility for screen readers by providing text descriptions for icon buttons that lack visible text labels.
♿ Accessibility:

• Added aria-label="Delete filter group" to the delete group button.
• Added aria-label="Reset settings" to the reset button in Graph Controls.
• Added aria-label="Close panel" to the close button in Graph Controls.
• Added aria-label="Toggle Line Wrap" to the text wrap button in the Code Block editor extension.
• Added aria-label={copied ? "Code copied" : "Copy Code"} to the copy button in the Code Block editor extension.

---

PR created automatically by Jules for task 6199644146198018699 started by @threehymns

[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!

New to Jules? Learn more at jules.google/docs.

---

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