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Remove outdated checkout-completion-flow-documentation.md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/utils/scroll-position/README.md

@@ -2,7 +2,16 @@
 
 ## Overview
 
-Provides utilities for storing, restoring, and observing scroll position across navigation or component view changes.
+The `@isa/utils/scroll-position` library provides a comprehensive set of utilities for managing scroll position persistence and viewport visibility detection across route navigation and component lifecycle changes. It enables seamless user experience by automatically preserving and restoring scroll positions when users navigate between views, particularly useful in list/detail navigation patterns.
+
+**Key Features:**
+- **Automatic Scroll Restoration**: Preserve and restore scroll position across route navigation
+- **Session Storage Integration**: Persists scroll positions in session storage for reliability
+- **Route-Level Control**: Enable/disable restoration per route via route data configuration
+- **Viewport Detection**: Observe when elements enter or leave the viewport for lazy loading and infinite scroll
+- **Configurable Delays**: Control timing of scroll restoration with optional delays
+
+**Type:** Utility library with functions, injectables, and directives
 
 ## Features