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.config.cjs

@@ -0,0 +1,4 @@
+module.exports = {
+    testEnvironment: 'node',
+    testMatch: ['**/__tests__/**/*.test.js'],
+};