feat(baoyu-cover-image): add screen-print rendering and duotone palette

Add screen-print as 7th rendering style with halftone textures and limited
colors. Add duotone as 10th color palette for dramatic two-color compositions.
Update all compatibility matrices and style presets (poster-art, mondo,
art-deco, propaganda, cinematic).

skills/baoyu-cover-image/references/palettes/duotone.md

@@ -0,0 +1,39 @@
+# duotone
+
+Dramatic, cinematic, two-color high contrast
+
+## Color Palette
+
+| Role | Color | Hex |
+|------|-------|-----|
+| Primary 1 | Burnt Orange | #E8751A |
+| Primary 2 | Deep Teal | #0A6E6E |
+| Background | Off-Black | #121212 |
+| Background Alt | Dark Charcoal | #1E1E1E |
+| Accent 1 | Warm Cream | #F5E6D0 |
+| Accent 2 | Amber Highlight | #F4A623 |
+
+## Duotone Pair Options
+
+Choose ONE pair based on content mood. The two colors dominate the entire image:
+
+| Pair | Color A | Color B | Feel |
+|------|---------|---------|------|
+| Orange + Teal | #E8751A | #0A6E6E | Cinematic, action |
+| Red + Cream | #C0392B | #F5E6D0 | Bold, classic |
+| Blue + Gold | #1A3A5C | #D4A843 | Prestigious, premium |
+| Purple + Green | #6B3FA0 | #2ECC71 | Futuristic, contrast |
+| Magenta + Cyan | #C2185B | #00BCD4 | Vibrant, pop |
+| Crimson + Navy | #DC143C | #0D1B2A | Dramatic, noir |
+
+## Decorative Hints
+
+- Stark two-color separation across entire composition
+- Halftone transitions between the two colors
+- Silhouettes in one color against the other
+- Minimal use of third color (only for small highlights)
+- High contrast figure-ground relationships
+
+## Best For
+
+Movie posters, album covers, concert prints, dramatic announcements, cinematic content, bold branding, editorial covers, artistic campaigns