refactor(baoyu-article-illustrator): extract content to reference files

- Simplify SKILL.md by extracting usage and prompt templates
- Add references/usage.md for command syntax
- Add references/prompt-construction.md for prompt templates
- Add default_output_dir preference option
- Reorganize workflow from 5 to 6 steps with Pre-check phase

skills/baoyu-article-illustrator/references/config/preferences-schema.md

@@ -23,6 +23,8 @@ preferred_style:
 
 language: null            # zh|en|ja|ko|auto
 
+default_output_dir: null  # same-dir|illustrations-subdir|independent
+
 custom_styles:
   - name: my-style
     description: "Style description"
@@ -48,6 +50,7 @@ custom_styles:
 | `preferred_style.name` | string | null | Style name or null |
 | `preferred_style.description` | string | "" | Custom notes/override |
 | `language` | string | null | Output language (null = auto-detect) |
+| `default_output_dir` | enum | null | Output directory preference (null = ask each time) |
 | `custom_styles` | array | [] | User-defined styles |
 
 ## Position Options
@@ -59,6 +62,14 @@ custom_styles:
 | `bottom-center` | Bottom center |
 | `top-right` | Upper right corner |
 
+## Output Directory Options
+
+| Value | Description |
+|-------|-------------|
+| `same-dir` | Same directory as article |
+| `illustrations-subdir` | `{article-dir}/illustrations/` subdirectory |
+| `independent` | `illustrations/{topic-slug}/` in working directory |
+
 ## Custom Style Fields
 
 | Field | Required | Description |

skills/baoyu-article-illustrator/references/prompt-construction.md

@@ -0,0 +1,127 @@
+# Prompt Construction
+
+## Principles
+
+Good prompts must include:
+
+1. **Layout Structure First**: Describe composition, zones, flow direction
+2. **Specific Data/Labels**: Use actual numbers, terms from article
+3. **Visual Relationships**: How elements connect
+4. **Semantic Colors**: Meaning-based color choices (red=warning, green=efficient)
+5. **Style Characteristics**: Line treatment, texture, mood
+6. **Aspect Ratio**: End with ratio and complexity level
+
+## Type-Specific Templates
+
+### Infographic
+
+```
+[Title] - Data Visualization
+
+Layout: [grid/radial/hierarchical]
+
+ZONES:
+- Zone 1: [data point with specific values]
+- Zone 2: [comparison with metrics]
+- Zone 3: [summary/conclusion]
+
+LABELS: [specific numbers, percentages, terms from article]
+COLORS: [semantic color mapping]
+STYLE: [style characteristics]
+ASPECT: 16:9
+```
+
+### Scene
+
+```
+[Title] - Atmospheric Scene
+
+FOCAL POINT: [main subject]
+ATMOSPHERE: [lighting, mood, environment]
+MOOD: [emotion to convey]
+COLOR TEMPERATURE: [warm/cool/neutral]
+STYLE: [style characteristics]
+ASPECT: 16:9
+```
+
+### Flowchart
+
+```
+[Title] - Process Flow
+
+Layout: [left-right/top-down/circular]
+
+STEPS:
+1. [Step name] - [brief description]
+2. [Step name] - [brief description]
+...
+
+CONNECTIONS: [arrow types, decision points]
+STYLE: [style characteristics]
+ASPECT: 16:9
+```
+
+### Comparison
+
+```
+[Title] - Comparison View
+
+LEFT SIDE - [Option A]:
+- [Point 1]
+- [Point 2]
+
+RIGHT SIDE - [Option B]:
+- [Point 1]
+- [Point 2]
+
+DIVIDER: [visual separator]
+STYLE: [style characteristics]
+ASPECT: 16:9
+```
+
+### Framework
+
+```
+[Title] - Conceptual Framework
+
+STRUCTURE: [hierarchical/network/matrix]
+
+NODES:
+- [Concept 1] - [role]
+- [Concept 2] - [role]
+
+RELATIONSHIPS: [how nodes connect]
+STYLE: [style characteristics]
+ASPECT: 16:9
+```
+
+### Timeline
+
+```
+[Title] - Chronological View
+
+DIRECTION: [horizontal/vertical]
+
+EVENTS:
+- [Date/Period 1]: [milestone]
+- [Date/Period 2]: [milestone]
+
+MARKERS: [visual indicators]
+STYLE: [style characteristics]
+ASPECT: 16:9
+```
+
+## What to Avoid
+
+- Vague descriptions ("a nice image")
+- Literal metaphor illustrations
+- Missing concrete labels/annotations
+- Generic decorative elements
+
+## Watermark Integration
+
+If watermark enabled in preferences, append:
+
+```
+Include a subtle watermark "[content]" positioned at [position] with approximately [opacity*100]% visibility.
+```

skills/baoyu-article-illustrator/references/usage.md

@@ -0,0 +1,66 @@
+# Usage
+
+## Command Syntax
+
+```bash
+# Auto-select type and style based on content
+/baoyu-article-illustrator path/to/article.md
+
+# Specify type
+/baoyu-article-illustrator path/to/article.md --type infographic
+
+# Specify style
+/baoyu-article-illustrator path/to/article.md --style blueprint
+
+# Combine type and style
+/baoyu-article-illustrator path/to/article.md --type flowchart --style notion
+
+# Specify density
+/baoyu-article-illustrator path/to/article.md --density rich
+
+# Direct content input (paste mode)
+/baoyu-article-illustrator
+[paste content]
+```
+
+## Options
+
+| Option | Description |
+|--------|-------------|
+| `--type <name>` | Illustration type (see Type Gallery in SKILL.md) |
+| `--style <name>` | Visual style (see references/styles.md) |
+| `--density <level>` | Image count: minimal / balanced / rich |
+
+## Input Modes
+
+| Mode | Trigger | Output Directory |
+|------|---------|------------------|
+| File path | `path/to/article.md` | Use `default_output_dir` preference, or ask if not set |
+| Paste content | No path argument | `illustrations/{topic-slug}/` |
+
+## Output Directory Options
+
+| Value | Path |
+|-------|------|
+| `same-dir` | `{article-dir}/` |
+| `illustrations-subdir` | `{article-dir}/illustrations/` |
+| `independent` | `illustrations/{topic-slug}/` |
+
+Configure in EXTEND.md: `default_output_dir: illustrations-subdir`
+
+## Examples
+
+**Technical article with data**:
+```bash
+/baoyu-article-illustrator api-design.md --type infographic --style blueprint
+```
+
+**Personal story**:
+```bash
+/baoyu-article-illustrator journey.md --type scene --style warm
+```
+
+**Tutorial with steps**:
+```bash
+/baoyu-article-illustrator how-to-deploy.md --type flowchart --density rich
+```