🎯 Update progress on GamemasterExplorer refactoring with new composable for line selection and additional tests

docs/projects/Pokedex.Online/PROGRESS.md

@@ -121,7 +121,7 @@ Last Updated: January 28, 2026
 
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-## Phase 5: GamemasterExplorer Refactoring (2/9 complete)
+## Phase 5: GamemasterExplorer Refactoring (3/9 complete)
 **Duration**: 5-7 days  
 **Status**: In Progress  
 **Target**: Reduce from 1627 lines → ~400 lines (76% reduction)
@@ -139,12 +139,18 @@ Last Updated: January 28, 2026
 - [x] Extract file methods (loadStatus, loadFile, clearFileSelection, updateDisplayLines)
 - [x] Support pagination and virtual scrolling preparation
 - [x] Write comprehensive tests - 45 tests passing ✅
-  - File loading for all types (pokemon, moves, allForms, raw)
-  - File size validation (50MB limit for raw files)
-  - Display line pagination (10K lines initially)
-  - Preference persistence
-  - JSON path extraction for filtering
-  - Error handling and state management
+
+### ✅ Step 15: Extract useLineSelection Composable
+- [x] Create `src/composables/useLineSelection.js` - Line selection and export
+- [x] Extract selection state (selectedLines with Set data structure)
+- [x] Support single, range, and multi-select (Shift/Ctrl modifiers)
+- [x] Extract methods (toggleLineSelection, clearSelection, selectAll, invertSelection)
+- [x] Copy/export functionality (to clipboard and files)
+- [x] Write comprehensive tests - 25 tests passing ✅
+  - Single and range selection with keyboard modifiers
+  - Clipboard and file export operations
+  - Selection state and computed properties
+  - URL sharing functionality
 
 ### ⏳ Step 14: Extract useGamemasterFiles Composable
 - [ ] Create `src/composables/useGamemasterFiles.js`