docs: correct the delta field the MAF streaming example reads

[examon]

Fixes #2104

The "Node.js / TypeScript (standalone SDK)" example under Streaming responses in the Microsoft Agent Framework guide registered an assistant.message_delta handler that read event.data.delta. The payload type for that event, AssistantMessageDeltaData, declares deltaContent; there is no delta. The read therefore evaluated to undefined, the ?? "" fallback turned that into an empty string, and the handler wrote nothing for each delta event.

The change

 session.on("assistant.message_delta", (event) => {
-    process.stdout.write(event.data.delta ?? "");
+    process.stdout.write(event.data.deltaContent ?? "");
 });

docs/integrations/microsoft-agent-framework.md, one line. event.data.delta appeared exactly once in the repository; it now appears nowhere.

deltaContent is required, so the ?? "" fallback is inert either way. It is kept as-is to hold the change to the single field name.

Why deltaContent

AssistantMessageDeltaData (nodejs/src/generated/session-events.ts) declares deltaContent, messageId and an optional deprecated parentToolCallId. The generated types for Go, .NET, Java and Python agree on the same wire field, and the Java example in this same section of this same guide already calls event.getData().deltaContent().

Verification

Extracting the doc block and type-checking it against the SDK source types, with the compiler options scripts/docs-validation/validate.ts generates:

• before: snippet.ts(11,37): error TS2339: Property 'delta' does not exist on type 'AssistantMessageDeltaData'. (exit 2)
• after: no diagnostics (exit 0)

That is the block's only type error, and this change removes it.

Observed behaviour, using an instrumented handler that accumulates both accessors side by side rather than the doc block verbatim:

payload keys:           ["messageId","deltaContent"]
event.data.delta:       ""
event.data.deltaContent: "pong"

Checks run in nodejs/: npm run lint, npm run typecheck, npm run format:check and npm test all pass.

[Copilot]

Pull request overview

Corrects the Microsoft Agent Framework TypeScript streaming example to read the actual delta payload field.

Changes:

• Replaces nonexistent event.data.delta with event.data.deltaContent.

Show a summary per file

File	Description
docs/integrations/microsoft-agent-framework.md	Fixes streamed response output in the standalone SDK example.

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