🎨 Palette: Add tooltips explaining disabled bulk action buttons

[mapleleaflatte03]

💡 What:
Wrapped disabled bulk action buttons in a focusable span with a native tooltip to explain why they are disabled, and dynamically toggle the attributes via JS when they become enabled. Added a learning to .jules/palette.md.

🎯 Why:
To make the operator interface more intuitive by explaining disabled states, and to improve accessibility for screen readers and keyboard users who would otherwise not hear or be able to focus the disabled elements.

📸 Before/After:
Before: Disabled buttons silently failed to provide tooltips on hover because they don't capture pointer events.
After: Disabled buttons now display "Select items to apply bulk decision" on hover and on keyboard focus.

♿ Accessibility:
The buttons are wrapped in a focusable span with tabindex="0" when disabled so keyboard users can navigate to them and read the title. When enabled, the wrapper's title and tabindex are dynamically removed to avoid confusing double tab-stops.

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PR created automatically by Jules for task 14306601515672726792 started by @mapleleaflatte03

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