fix(storage): populate cache before write buffer for read-after-write consistency

Cloud storage adapters (GCS, S3, R2, Azure) use write buffers in
high-volume mode to batch network operations. However, the cache was
not being populated when items were added to the buffer, causing
add() to return successfully but immediate relate() calls to fail
with "Source entity not found".

This fix ensures the cache is populated BEFORE adding to the write
buffer, guaranteeing read-after-write consistency even when writes
are buffered for asynchronous flushing.

Affected adapters:
- GcsStorage: saveNode, saveEdge
- S3CompatibleStorage: saveNode
- R2Storage: saveNode, saveEdge
- AzureBlobStorage: saveNode, saveEdge

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/storage/adapters/s3CompatibleStorage.ts

@@ -1069,6 +1069,14 @@ export class S3CompatibleStorage extends BaseStorage {
     // Use write buffer in high-volume mode
     if (this.highVolumeMode && this.nounWriteBuffer) {
       this.logger.trace(`📝 BUFFERING: Adding noun ${node.id} to write buffer (high-volume mode active)`)
+
+      // v6.2.6: CRITICAL FIX - Populate cache BEFORE buffering for read-after-write consistency
+      // Without this, add() returns but relate() can't find the entity (cloud storage production bug)
+      // The buffer flushes asynchronously, but cache ensures immediate reads succeed
+      if (node.vector && Array.isArray(node.vector) && node.vector.length > 0) {
+        this.nounCacheManager.set(node.id, node)
+      }
+
       await this.nounWriteBuffer.add(node.id, node)
       return
     } else if (!this.highVolumeMode) {