Implement SetHighlightedFunc (#6)

[cassdeckard]

Summary

Implements #6 SetHighlightedFunc for TextView with region support.

Changes

• Config: Add onHighlighted field to Primitive for TextView with regions: true
• Builder: Wire SetHighlightedFunc in PropertyMapper; sets __highlightedRegion before running the template callback
• Builtin: Add showHighlightedNotification to display the selected region number
• Example: Extend textview.yaml with onHighlighted demo and status display
• Docs: Document onHighlighted and __highlightedRegion in tview-coverage.md
• Tests: Add TestApplyTextViewProperties_OnHighlighted and TestBuildFlex_TextViewWithOnHighlighted

Usage

primitive:
  type: textView
  regions: true
  text: '["slide1"]Slide 1[""] ["slide2"]Slide 2[""]'
  onHighlighted: '{{ switchToPage "{{ bindState __highlightedRegion }}" }}'

Enables presentation-style info bar navigation where clicking/selecting a region switches pages.

[github-actions]

Test Results

245 tests  +2   245 ✅ +2   0s ⏱️ ±0s
  5 suites ±0     0 💤 ±0 
  1 files   ±0     0 ❌ ±0 

Results for commit 0e1bb30. ± Comparison against base commit d06bc34.

♻️ This comment has been updated with latest results.