feat: add flat-doodle style to cover-image and article-illustrator

Add new flat-doodle style featuring:
- Bold black outlines
- Bright pastel colors (pink, mint, lavender, yellow)
- Simple flat shapes with cute rounded proportions
- White background
- Best for productivity, SaaS, workflow content

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

skills/baoyu-cover-image/SKILL.md

@@ -47,6 +47,7 @@ Generate hand-drawn style cover images for articles with multiple style options.
 | Style | Description |
 |-------|-------------|
 | `elegant` (Default) | Refined, sophisticated, understated |
+| `flat-doodle` | Bold outlines, pastel colors, cute rounded shapes |
 | `blueprint` | Technical schematics, engineering precision |
 | `bold-editorial` | Magazine cover impact, dramatic typography |
 | `chalkboard` | Black chalkboard, colorful chalk drawings |
@@ -87,6 +88,7 @@ When no `--style` is specified, the system analyzes content to select the best s
 | Nature, eco, wellness, health, organic | `nature` |
 | Pop culture, 80s/90s nostalgia, badges | `retro` |
 | Product, SaaS, dashboard, productivity | `notion` |
+| Productivity, workflow, app, tools, cute | `flat-doodle` |
 | Gaming, retro tech, developer, 8-bit | `pixel-art` |
 | Educational, tutorial, knowledge sharing | `sketch-notes` |
 | Creative proposals, brand, toy-like | `vector-illustration` |

skills/baoyu-cover-image/references/styles/flat-doodle.md

@@ -0,0 +1,27 @@
+# flat-doodle
+
+Cute, simple doodle illustrations with bold outlines
+
+## Color Palette
+
+- Primary: Bright pastel pink (#FFB6C1), mint (#98D8C8), lavender (#C8A2C8), butter yellow (#FFFACD)
+- Background: Clean white (#FFFFFF)
+- Accents: Bold black outlines, soft coral, sky blue
+
+## Visual Elements
+
+- Bold black outlines around all shapes
+- Simple flat shapes with no shading
+- Cute rounded proportions
+- Productivity-themed icons
+- Isolated elements on white background
+- Minimal decorative details
+
+## Typography
+
+- Simple, clean sans-serif or hand-lettering
+- Bold and easily readable
+
+## Best For
+
+Productivity content, SaaS articles, workflow tutorials, app features, beginner guides, casual business