🎨 Palette: Add accessible progressive character limit feedback

[Sczitzo]

💡 What: Added dynamic character limit counter for the alternative thought textarea that turns orange when approaching the limit (80%) and red when very close (90%) or at the limit.
🎯 Why: A static counter forces users to do mental math. The color changes give immediate visual cues without needing to constantly check the numbers, lowering cognitive load.
📸 Before/After: Visuals provided in verification steps show the transition through gray -> orange -> red as the limit is reached.
♿ Accessibility: Instead of using aria-live on the counter numbers (which spams screen readers on every keystroke), the implementation conditionally mounts visually hidden elements with role="status" at specific thresholds (80%, 90%, 100%) providing clean, infrequent warnings only when necessary.

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PR created automatically by Jules for task 13102679281359739658 started by @Sczitzo

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