📝 docs: cherry-pick 6 focused guides from PR #17 (CLI, CODE_EXAMPLES, HISTORY, OBSERVABILITY, ROADMAP, TROUBLESHOOTING)

documentation/HISTORY.md

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+# Development History
+
+This document records the historical development phases of `dance-lessons-coach`. Extracted from the original `AGENTS.md` (Tâche 6 restructure) for lazy-loading compatibility with Mistral Vibe (128k context).
+
+All phases below are **completed** ✅. They are kept here for traceability and onboarding context — refer to ADRs (`adr/`) for the technical decisions behind each phase.
+
+## Phase 1: Foundation
+
+- Go 1.26.1 environment setup
+- Project structure with `cmd/` and `pkg/` directories
+- Core Greet service implementation
+- CLI interface
+- Unit tests
+
+## Phase 2: Web API
+
+- Chi router integration
+- Versioned API endpoints (`/api/v1`)
+- Health endpoint (`/api/health`)
+- JSON responses with proper headers
+
+## Phase 3: Logging & Architecture
+
+- Zerolog integration with Trace level
+- Context-aware logging
+- Interface-based design patterns
+- Dependency injection
+
+## Phase 4: Documentation & Testing
+
+- Comprehensive `AGENTS.md`
+- `README.md` with usage instructions
+- Server management guide
+- API endpoint documentation
+
+## Phase 5: Configuration Management
+
+- Viper integration for configuration
+- Environment variable support with `DLC_` prefix
+- Customizable server host/port
+- Configurable shutdown timeout
+- Configuration validation and logging
+- Example configuration file
+
+## Phase 6: Graceful Shutdown
+
+- Context-aware server initialization
+- Signal-based termination (`SIGINT`, `SIGTERM`)
+- Configurable shutdown timeout
+- Readiness endpoint for Kubernetes/service mesh integration
+- Proper resource cleanup during shutdown
+- Health endpoint remains healthy during graceful shutdown
+
+## Phase 7: OpenTelemetry Integration
+
+- OpenTelemetry Go libraries integration
+- Jaeger compatibility for distributed tracing
+- Middleware-only approach using `otelhttp.NewHandler`
+- Configurable sampling strategies
+- Graceful shutdown of tracer provider
+- OTLP exporter with gRPC support
+
+## Phase 8: Build System & Documentation
+
+- Build script for binary compilation
+- Binary output to `bin/` directory
+- Comprehensive commit conventions with gitmoji reference
+- Updated documentation with Jaeger integration guide
+- Cleaned up configuration files
+- Enhanced logging configuration with file output support
+
+## Phase 9: Final Refinements
+
+- Removed unnecessary `time.Sleep` for log flushing
+- Changed server operational logs from Info to Trace level
+- Moved all logging setup logic to config package
+- Simplified server entrypoint to 27 lines
+- Verified all functionality with comprehensive testing
+- Updated documentation to reflect final architecture
+
+## Beyond Phase 9
+
+Subsequent work (CI/CD, BDD scenarios, ADR audit, JWT, config hot-reloading) is tracked in the [Changelog](../CHANGELOG.md) and the corresponding [ADRs](../adr/).