docs: update CHANGELOG and BREAKING for v0.9.11

BREAKING.md

@@ -4,6 +4,20 @@
 
 This document describes breaking changes in CTModels releases and how to migrate your code.
 
+## [0.9.11] - 2026-03-31
+
+### No Breaking Changes
+
+This version includes only internal improvements and code formatting enhancements:
+
+- Applied JuliaFormatter across entire codebase for consistent style
+- Enhanced CompatHelper workflow with subdirectories support
+- All existing APIs remain unchanged
+- Zero functional changes - formatting and maintenance only
+- Improved code maintainability and development experience
+
+---
+
 ## [0.9.10-beta] - 2026-03-17
 
 ### No Breaking Changes

CHANGELOG.md

@@ -7,6 +7,31 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.9.11] - 2026-03-31
+
+### 🔧 Internal Improvements
+
+#### Code Quality and Maintenance
+
+- **Code formatting**: Applied JuliaFormatter across entire codebase for consistent style
+- **Enhanced readability**: Improved code formatting in interpolation, serialization, and display modules
+- **Test formatting**: Updated test files for better maintainability
+- **Zero functional changes**: All APIs remain unchanged, formatting only
+
+#### Development Workflow
+
+- **CompatHelper enhancement**: Added subdirectories input to CompatHelper workflow for better dependency management
+- **Automated formatting**: Integrated JuliaFormatter in CI/CD pipeline
+- **Development tools**: Improved development experience with consistent code style
+
+### 📚 Documentation
+
+- **No breaking changes**: This release focuses on internal code quality
+- **Maintained compatibility**: All existing functionality preserved
+- **Enhanced maintainability**: Cleaner codebase for future development
+
+---
+
 ## [0.9.10-beta] - 2026-03-17
 
 ### 🎨 Documentation Enhancements