feat: Add OpenAI Batch API Instrumentation

.changeset/openai-batch-api-instrumentation.md

@@ -0,0 +1,5 @@
+---
+"braintrust": minor
+---
+
+feat: Add OpenAI Batch API Instrumentation

.changeset/update-platform-types.md

@@ -0,0 +1,5 @@
+---
+"braintrust": patch
+---
+
+chore: Update platform types

AGENTS.md

@@ -25,6 +25,10 @@ mise install        # Install toolchain and dependencies
 pnpm run build      # Build all workspace packages (from repo root)
 ```
 
+## Public API
+
+Keep public exports minimal. Generally, export only the requested runtime APIs and do not export types unless explicitly requested.
+
 ## Instrumentation
 
 Use the normal Orchestrion config plus plugin/channel path by default. Special-case source patches should be rare exceptions only when the target SDK cannot be instrumented through the standard transformer path, and the reason should be documented next to the patch.