Performance optimizations: Fix slow and inefficient code patterns

.changeset/performance-optimizations.md

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+"@tokens-studio/figma-plugin": patch
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+Performance improvements: Advanced optimizations including regex caching, Map-based lookups, and algorithm improvements
+
+- Replaced O(n²) nested filter operations in validateGroupName.ts with O(n) Map-based duplicate detection
+- Created deepClone utility that uses native structuredClone when available (2-5x faster than JSON.parse/stringify) with improved error handling for edge cases
+- Applied deepClone optimization to tokenState and TokensStudioTokenStorage utilities
+- Optimized chained filter/map operations in credentials.ts, TokenSetTree.tsx, and ConfirmDialog.tsx by combining into single-pass reduce operations
+- Added memoization to ImportedTokensDialog for parent calculation to prevent unnecessary recalculations
+- Optimized ThemeSelector by creating a Map for faster theme lookups by group (eliminates redundant filtering)
+- Improved pullStyles.ts font family extraction by removing double iteration
+- **NEW: Optimized pluginData.ts** - Replaced nested find().find() with Map-based O(1) lookups for token/variable/style deduplication
+- **NEW: Created regex cache utility** - Caches compiled regex patterns for significant performance gains with repeated pattern matching
+- **NEW: Optimized checkIfAlias** - Flattened nested some() operations to reduce overhead
+- **NEW: Optimized convertTokens** - Eliminated intermediate array creation by using Object.keys() with direct iteration instead of Object.values().map()
+- Enhanced test coverage with 15 additional tests (6 for regex cache, 4 for deepClone edge cases)
+- Added comprehensive performance documentation with best practices