**docs: add detailed concurrency analysis and implementation documentation**

- Introduced `CONCURRENCY_ANALYSIS.md` to outline identified concurrency issues, including statistics handling, index synchronization, and storage contention.
- Added `CONCURRENCY_IMPLEMENTATION_SUMMARY.md` to summarize concurrency improvements, such as distributed locking and change log mechanisms.
- Created `STORAGE_CONCURRENCY_ANALYSIS.md` to evaluate concurrency risks and applied solutions for different storage adapters (`S3CompatibleStorage`, `FileSystemStorage`, `OPFSStorage`, and `MemoryStorage`).
- Updated codebase with changes related to concurrency, including distributed locking, atomic updates, event-driven synchronization, and change log support.
- Refactored tests to verify behavior of new concurrency mechanisms, including robust error handling and cleanup functions.

**Purpose**: Provides comprehensive documentation and implementation details to ensure robust concurrency handling in multi-instance, high-throughput environments.

tests/storage-adapter-coverage.test.ts

@@ -174,15 +174,24 @@ const runStorageTests = (adapterName: string, createStorageAdapter: () => Promis
       // Clear the database
       await brainyInstance.clear()
       
+      // Debug: Check what's in the HNSW index after clear
+      const nounsInIndex = brainyInstance.index.getNouns()
+      if (nounsInIndex.size > 0) {
+        console.log(`HNSW index still has ${nounsInIndex.size} nouns after clear:`)
+        for (const [id, noun] of nounsInIndex) {
+          console.log(`  - ${id}: ${noun.text}`)
+        }
+      }
+      
       // Verify it's empty
-      let size = await brainyInstance.size()
+      let size = brainyInstance.size()
       expect(size).toBe(0)
       
       // Restore from backup
       await brainyInstance.restore(backup)
       
       // Verify data was restored
-      size = await brainyInstance.size()
+      size = brainyInstance.size()
       expect(size).toBe(2)
       
       // Verify specific items