🎨 Palette: [a11y] Make sitrep anchor tags accessible as modal buttons

[0m364]

💡 What: Added role="button" and aria-haspopup="dialog" to #sitrep-btn links and enabled keyboard activation via spacebar.
🎯 Why: Using <a> tags for modals confuses screen readers and prevents keyboard users from triggering them with the spacebar.
📸 Before/After: Visuals unchanged; interactions significantly improved for keyboard users.
♿ Accessibility: Ensures the element is correctly identified as a modal-triggering button and supports full keyboard functionality (Space/Enter).

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PR created automatically by Jules for task 14402454324665044574 started by @0m364

[google-labs-jules]

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