Add check-code-style skill - Code formatting utility

- Level 1 utility skill
- ktlint auto-formatting
- Style rules documentation (2-space indent, trailing commas)
- Integration with CI/CD

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

Author: Canato

.claude/skills/check-code-style.md

@@ -0,0 +1,88 @@
+---
+name: check-code-style
+description: Check and fix code style with ktlint
+argument-hint: "[action: format|check]"
+level: 1
+triggers:
+  - "format"
+  - "ktlint"
+  - "check style"
+  - "fix style"
+---
+
+# Check Code Style Skill
+
+Check and automatically fix code style issues using ktlint.
+
+## Usage
+
+Run this skill before committing code to ensure style compliance.
+
+## Commands
+
+### Auto-Fix Code Style
+```bash
+./gradlew ktlintFormat
+```
+
+### Check Code Style (No Auto-Fix)
+```bash
+./gradlew ktlint
+```
+
+### Check Specific Module
+```bash
+./gradlew :cropper:ktlint
+```
+
+## Style Rules
+
+This project uses:
+- **ktlint 1.3.1**
+- **IntelliJ IDEA code style**
+- **2-space indentation**
+- **Trailing commas enabled**
+- **Experimental ktlint features enabled**
+
+See `.editorconfig` for specific rule configuration.
+
+## Common Style Issues
+
+### Indentation
+**Rule**: 2 spaces, no tabs
+**Fix**: Run `./gradlew ktlintFormat`
+
+### Trailing Commas
+**Rule**: Allowed and encouraged
+**Example**:
+```kotlin
+// Good
+listOf(
+  "one",
+  "two",
+  "three", // Trailing comma OK
+)
+
+// Also OK
+listOf("one", "two", "three")
+```
+
+### Import Order
+**Fix**: Auto-fixed by ktlintFormat
+
+### Line Length
+**Rule**: Disabled (no max length)
+**Note**: Still keep lines reasonable for readability
+
+## What to Check
+
+After running ktlintFormat:
+1. ✅ Review the changes made
+2. ✅ Ensure formatting is correct
+3. ✅ Run `./gradlew ktlint` to verify
+4. ✅ Commit the formatted code
+
+## Integration with Build
+
+ktlint runs automatically in CI/CD pipeline.
+Always run locally before pushing.