🎨 Palette: Add ARIA labels to icon-only buttons

[threehymns]

🎨 Palette: Add ARIA labels to icon-only buttons

💡 What: Added aria-label attributes to icon-only buttons in graph-tab.tsx (Reset settings, Close panel, Delete group) and code-block-codemirror.tsx (Toggle Line Wrap, Copy Code, Language Select). Also added title attributes where missing.
🎯 Why: Icon-only buttons without explicit labels are inaccessible to screen reader users. Adding aria-label provides the necessary context for assistive technologies. Adding title provides a tooltip for mouse users.
📸 Before/After: No visual changes.
♿ Accessibility: Screen readers can now properly announce the function of these utility buttons.

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PR created automatically by Jules for task 2855680508320250666 started by @threehymns

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