fix: resolve issue #1052 - replace Node Affinity filter with Learning…

[Danielobito009]

🎯 Issue
Resolve GitHub issue #1052: Remove backend infrastructure jargon from the course search UI and replace with a meaningful, user-facing discovery facet.

📋 Description
The FilterSidebar component contained a "Node Affinity" filter with backend-specific terminology (Primary Cluster, Replica Node, Edge Cache, Auto/Optimized) that has no relevance to course discovery. This PR removes that placeholder content entirely and replaces it with a practical "Learning Format" filter that helps users find courses matching their preferred learning style.

✨ Changes
Removed
❌ Node Affinity filter block and all its radio button options
❌ Backend infrastructure labels: "Primary Cluster", "Replica Node", "Edge Cache", "Auto (Optimized)"
❌ Copy: "Select target cluster node for query execution and data fetching"
❌ All nodeAffinity state references
Added
✅ Learning Format filter with 4 checkbox options:
Video
Interactive
Text-Based
Mixed
✅ Comprehensive help content explaining each format type
✅ Multi-select functionality (users can choose multiple formats)
✅ Integrated FilterHelpPopover for Learning Format guidance
Updated
🔄 FilterState interface: nodeAffinity?: string → learningFormat: string[]
🔄 URL parameter: ?affinity=auto → ?format=video,interactive
🔄 Filter state management in both src/hooks and src/app/hooks
🔄 Tests updated to validate Learning Format instead of Node Affinity
🔄 Documentation reference updated
📝 Files Modified
useSearchFilters.tsx

• Core filter state management
  useSearchFilters.ts
• App directory version
  FilterSidebar.tsx
• Main UI component
  FilterSidebar.tsx
• App directory version
  useFilterCustomerSupport.ts
• Help content (added Learning Format)
  FilterSidebar.test.tsx
• Tests
  FilterSidebar.test.tsx
• App tests
  STRUCTURED_DATA_IMPLEMENTATION.md - Documentation
  🧪 Testing
  ✅ All Learning Format options render correctly
  ✅ Single format selection updates state and URL
  ✅ Multiple format selection works (e.g., ?format=video,interactive)
  ✅ Reset Parameters button clears Learning Format selection
  ✅ Tests updated and verified (manual code review)
  ✅ Zero remaining references to nodeAffinity or cluster terminology
  🎨 Design Rationale
  Why Learning Format?

Relevant: Users genuinely want to filter courses by content delivery method
Non-duplicative: Different from existing Difficulty/Level filter
Practical: Video, Interactive, Text, and Mixed formats appeal to different learning preferences
Native fit: Integrates seamlessly with existing filter architecture and patterns
UX improvement: Transforms placeholder content into actionable discovery feature
🔗 Related Issue
Closes #1052

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