chore: add Claude Code infrastructure and documentation system

Add comprehensive Claude Code tooling:
- Agents: docs-researcher, docs-researcher-advanced for documentation research
- Commands: dev:add-e2e-attrs, docs:library, docs:refresh-reference, quality:bundle-analyze, quality:coverage
- Skills: 8 specialized skills including api-change-analyzer, architecture-enforcer, library-scaffolder, and more

Update documentation:
- Comprehensive CLAUDE.md overhaul with library reference system
- Update testing guidelines in docs/guidelines/testing.md
- Update READMEs for checkout, icons, scanner, and scroll-position libraries

Remove outdated checkout-completion-flow-documentation.md

Update .gitignore for Claude Code files

libs/shared/scanner/README.md

@@ -2,7 +2,15 @@
 
 ## Overview
 
-The Scanner library provides barcode scanning capabilities for the ISA application using the [Scandit SDK](https://www.scandit.com/). It offers a complete solution for mobile barcode scanning with support for various barcode formats, ready-state detection, and seamless form integration.
+The `@isa/shared/scanner` library provides enterprise-grade barcode scanning capabilities for the ISA application using the [Scandit SDK](https://www.scandit.com/). It offers a complete, production-ready solution for mobile barcode scanning with comprehensive support for multiple symbologies, platform detection (iOS/Android), ready-state management, and seamless integration with Angular forms and reactive patterns.
+
+**Key Use Cases:**
+- Barcode scanning for product lookup and inventory management
+- Order processing and verification
+- Returns and remission workflows
+- Asset tracking and identification
+
+**Type:** Shared component library with services, directives, and ready-to-use UI components
 
 ## Features