docs(customization): document the Theme Editor, import and theme sync

[datlechin]

Documents TableProApp/TablePro#3452.

• Appearance: the mode is per Mac, the Themes list (Custom, Not Loaded, Built-in), drag and drop, Move to Trash with undo, and the 12 new built-in themes.
• Theme Editor window: preview, slot rows, reset, undo, Revert Changes, read-only built-ins.
• VS Code theme import: what maps and what does not, include rules and limits.
• Theme files: every slot optional, opaque backgrounds, fallbacks, what lands in Not Loaded.
• iCloud sync: custom themes and the light and dark choice sync; Appearance mode does not.
• Settings: the Appearance default reads System; the Plugins card no longer mentions themes.
• New Appearance pane screenshots, light and dark.

[mintlify]

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Project	Status	Preview	Updated
TablePro	🟢 Ready	View Preview	Oct 16, 2026, 4:01 PM

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