docs: Add comprehensive toast notification test and documentation

Test Addition:
- Created tests/mjs/29-pdf-toast-notifications.test.mjs (22 assertions)
- Validates toast elements, JavaScript API, animations
- Tests both PDF download scenarios (modal stays open vs. closes early)
- Verifies toast lifecycle: prepare → progress → success → dismiss
- Tests icon/title/message updates and progress bar animation

Test Coverage:
✅ Toast DOM elements exist
✅ JavaScript functions available (showPDFToast, hidePDFToast)
✅ Manual toast trigger and auto-hide
✅ PDF modal integration - Scenario A (stay in modal)
✅ PDF modal integration - Scenario B (close modal, toast appears)
✅ Toast content updates (📥 → ✅)
✅ Progress bar animation
✅ CSS animations defined (toastSlideIn, toastLifecycle, progressShrink)

Documentation Addition:
- Created doc/13-TOAST-NOTIFICATIONS.md (comprehensive guide)
- Architecture and component structure
- User experience flows (2 scenarios documented)
- JavaScript API reference (showPDFToast, hidePDFToast, showError)
- CSS structure and animations
- Template structure with ARIA accessibility
- PDF download integration details
- Accessibility features and testing guide
- Customization guide and troubleshooting

Documentation Updates:
- Updated doc/README.md (added entry #13, total: 12 → 13 docs)
- Updated tests/README.md (test count: 27 → 28)
- Updated tests/TEST-SUMMARY.md (added toast notifications coverage)
- Updated tests/mjs/README.md (added test 29 description)

Test Count: 28 active tests
Doc Count: 13 core documents
Coverage: Complete UX feedback system with dual-mode operation

tests/mjs/README.md

@@ -1,6 +1,6 @@
 # CV Project Test Suite (Active Tests)
 
-**27 comprehensive tests** covering all functionality from UI interactions to PDF generation.
+**28 comprehensive tests** covering all functionality from UI interactions to PDF generation.
 
 ## Quick Start
 
@@ -92,6 +92,17 @@ Final course icon validation
 ### 28-references-pdf-download.test.mjs
 References section PDF download button
 
+### 29-pdf-toast-notifications.test.mjs
+Toast notification system for PDF downloads
+- Toast elements exist in DOM
+- JavaScript functions available (showPDFToast, hidePDFToast)
+- Manual toast trigger and auto-hide
+- PDF modal integration - Scenario A (Stay in modal)
+- PDF modal integration - Scenario B (Close modal early, toast appears)
+- Toast content updates (preparing → success)
+- Progress bar animation
+- CSS animations defined (toastSlideIn, toastLifecycle, progressShrink)
+
 ## Migration Tests
 
 ### test-preference-migration.test.mjs
@@ -139,6 +150,6 @@ bun tests/mjs/28-references-pdf-download.test.mjs
 ---
 
 **Last Updated**: 2025-11-20
-**Test Count**: 27 active tests
-**Coverage**: Complete functionality coverage
+**Test Count**: 28 active tests
+**Coverage**: Complete functionality coverage including toast notifications
 **Status**: Production specification