Fixes #9: Parser performance optimizations

- Pre-compile all regex patterns as module-level constants in parser.js and jsonRepair.js
- Add format detection caching (lastDetectedFormat, formatCacheHits) to skip redundant checks
- Add clearFormatCache() export for cache invalidation
- Add comprehensive test suite (33 tests) for parser and jsonRepair modules
- Fix regex escaping in dynamic patterns (statRegex, fieldRegex)
- Improve toFieldKey() regex specificity

jest.setup.cjs

@@ -0,0 +1,22 @@
+// Jest setup file - set up mocks before tests run
+const mockState = {
+    extensionSettings: {
+        debugMode: false,
+        userStats: {},
+        trackerConfig: {},
+        quests: { main: '', optional: [] }
+    },
+    FEATURE_FLAGS: { useNewInventory: false },
+    addDebugLog: () => {}
+};
+
+const mockPersistence = {
+    saveSettings: () => {}
+};
+
+const mockInventoryParser = {
+    extractInventory: () => null
+};
+
+// We can't easily mock ESM imports in Jest without transform
+// Instead, we'll create mock files that Jest can use