Phase 3: Consolidate global state into AppState object

- #28: Created centralized AppState object consolidating 11 global variables
- Organized state into logical sections:
  * focusTraps (includeEditor, validationReport, diffReport)
  * Configuration data (publishers, copyrights, selectedCopyrights)
  * Include blocks (includeBlocks, currentEditingIncludeId)
  * Form state (hasUnsavedChanges, originalLoadedValueSet)
  * Drag and drop (draggedElement, draggedIncludeElement)
  * Preview debouncing (updatePreviewTimeoutId)
- Replaced ~102 references throughout codebase
- Reduced global variables from 11 to 1
- Improves code organization and maintainability

Completes Option C (Enhanced Single File) implementation.
All 6 medium-priority tasks now complete (#25, #26, #27, #28, #29, #31).

Resolves #28

Co-Authored-By: Claude Code - Sonnet 4.5 <anthropic.com>

Author: MattCordell

TODO.md

@@ -110,7 +110,7 @@ This document contains recommended enhancements for the FHIR ValueSet Creator, o
     - Theme Management
   - **Implementation**: Added 17 comprehensive section headers throughout 2,413 lines of JavaScript code: THEME MANAGEMENT, CONFIGURATION CONSTANTS, FOCUS MANAGEMENT & ACCESSIBILITY, APPLICATION STATE, INITIALIZATION, PUBLISHER & COPYRIGHT CONFIGURATION, COPYRIGHT MANAGEMENT, INCLUDE BLOCK MANAGEMENT, FORM VALIDATION, FHIR VALUESET GENERATION, DIFF ENGINE, PREVIEW & UI UPDATES, PREVIEW DEBOUNCING, FILE SIZE VALIDATION, FILE I/O OPERATIONS, UI UTILITIES & HELPERS, and FILE LOADING. Dramatically improves code navigation and maintainability.
 
-- [ ] **Consolidate global state** ([#28](https://github.com/MattCordell/Stoker/issues/28))
+✅ ~~**Consolidate global state**~~ ([#28](https://github.com/MattCordell/Stoker/issues/28)) **COMPLETED**
   - Create `AppState` object to wrap:
     - `includeBlocks`
     - `selectedCopyrights`
@@ -119,6 +119,7 @@ This document contains recommended enhancements for the FHIR ValueSet Creator, o
     - `publishers`
     - `copyrights`
   - Update all references throughout code
+  - **Implementation**: Created centralized AppState object at lines 1567-1594 consolidating 11 global variables into logical sections (focusTraps, configuration data, include blocks, form state, drag and drop, preview debouncing). Removed 3 scattered global variable declarations. Replaced ~102 references throughout the codebase using systematic pattern matching. Reduced global variables from 11 to 1, dramatically improving code organization and maintainability while preserving all functionality.
 
 ### Code Quality