🎨 Palette: Polish Preset Management UX and safety

[google-labs-jules]

This change improves the user experience of the Preset Management section in the tuning window. It adds visual hints, input validation, clearer feedback for disabled actions, and a safety gate for destructive operations.

Specific improvements:

1. New Preset Name Hint: Added "New Preset Name..." as a placeholder to the input field.
2. Save Validation: The "Save New" button is now disabled until a name is entered, with a tooltip explaining this requirement.
3. Accessibility: Tooltips for "Save" and "Delete" are now visible even when the buttons are disabled (using ImGuiHoveredFlags_AllowWhenDisabled), explaining why they are unavailable.
4. Safety Gate: The "Reset Defaults" button now requires two clicks within 3 seconds to execute, preventing accidental loss of all settings. The button label and tooltip change to "CONFIRM RESET?" during the confirmation window.

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PR created automatically by Jules for task 4105500410586990516 started by @coasting-nc

[google-labs-jules]

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