feat: add OpenAI batch memory indexing

docs/concepts/memory.md

@@ -108,6 +108,11 @@ agents: {
 If you don't want to set an API key, use `memorySearch.provider = "local"` or set
 `memorySearch.fallback = "none"`.
 
+Batch indexing (OpenAI only):
+- Set `agents.defaults.memorySearch.remote.batch.enabled = true` to submit embeddings via the OpenAI Batch API.
+- Default behavior waits for batch completion; tune `remote.batch.wait`, `remote.batch.pollIntervalMs`, and `remote.batch.timeoutMinutes` if needed.
+- Batch mode currently applies only when `memorySearch.provider = "openai"` and uses your OpenAI API key.
+
 Config example:
 
 ```json5
@@ -117,6 +122,9 @@ agents: {
       provider: "openai",
       model: "text-embedding-3-small",
       fallback: "openai",
+      remote: {
+        batch: { enabled: true }
+      },
       sync: { watch: true }
     }
   }