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/renderings/screen-print.md

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+# screen-print
+
+Bold, limited-color poster art with print texture
+
+## Core Characteristics
+
+Screen print / silkscreen aesthetic with flat color blocks, halftone textures, and deliberate print imperfections. Think Mondo limited-edition posters, vintage concert prints, and alternative movie poster art.
+
+## Lines
+
+- Clean, sharp edges between color blocks
+- No outlines — shapes defined by color boundaries
+- Stencil-cut quality, bold silhouettes
+- Geometric shapes with precise registration
+
+## Texture
+
+- Halftone dot patterns within color fills
+- Slight color layer misregistration (offset between print layers)
+- Paper grain texture beneath colors
+- Risograph / screen print imperfections (ink spread, dot gain)
+
+## Depth
+
+- Flat color planes layered front to back
+- Depth through silhouette overlap and color layering
+- No gradients — tonal variation via halftone density
+- Negative space as active compositional element
+
+## Element Vocabulary
+
+- Bold silhouettes and symbolic shapes
+- Geometric framing (circles, arches, triangles)
+- Figure-ground inversion (negative space forms secondary image)
+- Limited icon vocabulary: key props, symbolic objects
+- Typography integrated as design element, not overlay
+- Vintage poster border treatments
+
+## Typography Approach
+
+- Bold condensed sans-serif or hand-drawn lettering
+- Art Deco influences, vintage poster typography
+- Typography as integral part of composition (not separate layer)
+- Strong readability through high contrast with background