🎨 Palette: Add accessible progressive character limit warnings

[Sczitzo]

💡 What:
Updated the alternativeThought textarea's character counter to use progressively changing text colors (turning orange-700 at >= 240 chars, and red-600 at >= 270 chars). Added conditionally rendered, visually hidden elements with role="status" to announce character limits to screen readers at specific thresholds. Removed noisy real-time aria-live regions from the counter text to support better accessibility.

🎯 Why:
When users approach the 300 character limit, they need to be informed before their input is silently truncated. Visual users benefit from the progressive color change, while screen reader users need critical warnings (e.g., "Approaching character limit" or "Character limit reached") without having the raw number of characters announced loudly on every single keystroke.

📸 Before/After:
(Visual changes: the text '0 / 300 characters' starts gray, turns orange when >= 80% full, and red when >= 90% full. Screen readers now hear the static, concise warnings precisely when they approach or reach limits).

♿ Accessibility:
Implements a non-disruptive pattern for character limit warnings: uses static text rendered inside a visually hidden container with role="status" to prevent screen readers from interrupting typing with noisy counting announcements, while still ensuring they are immediately alerted when space runs low. Added an accompanying entry to .Jules/palette.md noting this improved technique.

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PR created automatically by Jules for task 6757001967933288236 started by @Sczitzo

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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Keep the status live region mounted before updating text

When the user types from 239 to 240 characters, this mounts a new role="status" element that already contains the warning text, rather than updating text inside an existing live region. Many screen reader/browser combinations only announce changes within a live region that was already present, so the first threshold warning can be missed; keep a single sr-only status element in the DOM and update its contents as the length crosses thresholds.

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