refactor(baoyu-article-illustrator): extract palette as independent third dimension

- Create palettes/ directory with macaron, warm, neon palette files
- Move macaron from styles/ to palettes/ (color scheme, not rendering style)
- Extract warm palette variant from vector-illustration into shared palette
- Add neon palette extracted from retro style colors
- Update architecture from Type × Style to Type × Style × Palette
- Add Palette Gallery and override rules to styles.md
- Add Palette Override section to prompt-construction.md
- Update presets table with Palette column
- Add palette selection step to workflow
- Add preferred_palette to EXTEND.md schema

skills/baoyu-article-illustrator/references/palettes/neon.md

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+# neon
+
+Vibrant neon colors on dark backgrounds
+
+## Background
+
+- Color: Deep Purple (#2D1B4E)
+- Texture: Subtle grid pattern or solid dark
+
+## Colors
+
+| Role | Color | Hex | Usage |
+|------|-------|-----|-------|
+| Background | Deep Purple | #2D1B4E | Primary background |
+| Alt Background | Dark Teal | #0F4C5C | Alternative sections |
+| Primary | Hot Pink | #FF1493 | Main accent |
+| Secondary | Electric Cyan | #00FFFF | Supporting elements |
+| Tertiary | Neon Yellow | #FFFF00 | Highlights |
+| Accent 1 | Lime Green | #32CD32 | Energy, success |
+| Accent 2 | Orange | #FF6B35 | Warmth |
+| Text | White | #FFFFFF | Text elements |
+
+## Accent
+
+Hot Pink (#FF1493) for primary emphasis. High contrast neon-on-dark creates immediate visual impact.
+
+## Best For
+
+Gaming, retro tech, 80s/90s nostalgic content, bold editorial, trend and pop culture