Add explicit LLM stream lifecycle events (#26722)

packages/llm/test/provider/anthropic-messages.test.ts

@@ -115,7 +115,7 @@ describe("Anthropic Messages route", () => {
         cacheReadInputTokens: 1,
         totalTokens: 7,
       })
-      expect(response.events.find((event) => event.type === "reasoning-delta" && event.text === "")).toMatchObject({
+      expect(response.events.find((event) => event.type === "reasoning-end")).toMatchObject({
         providerMetadata: { anthropic: { signature: "sig_1" } },
       })
       expect(response.events.at(-1)).toMatchObject({

packages/llm/test/provider/gemini.test.ts

@@ -204,9 +204,9 @@ describe("Gemini route", () => {
         totalTokens: 7,
       })
       expect(response.events).toEqual([
-        { type: "reasoning-delta", text: "thinking" },
-        { type: "text-delta", text: "Hello" },
-        { type: "text-delta", text: "!" },
+        { type: "reasoning-delta", id: "reasoning-0", text: "thinking" },
+        { type: "text-delta", id: "text-0", text: "Hello" },
+        { type: "text-delta", id: "text-0", text: "!" },
         {
           type: "request-finish",
           reason: "stop",

packages/llm/test/provider/openai-chat.test.ts

@@ -225,8 +225,8 @@ describe("OpenAI Chat route", () => {
 
       expect(response.text).toBe("Hello!")
       expect(response.events).toEqual([
-        { type: "text-delta", text: "Hello" },
-        { type: "text-delta", text: "!" },
+        { type: "text-delta", id: "text-0", text: "Hello" },
+        { type: "text-delta", id: "text-0", text: "!" },
         {
           type: "request-finish",
           reason: "stop",

packages/llm/test/provider/openai-responses.test.ts

@@ -336,8 +336,8 @@ describe("OpenAI Responses route", () => {
 
       expect(response.text).toBe("Hello!")
       expect(response.events).toEqual([
-        { type: "text-delta", id: "msg_1", text: "Hello", providerMetadata: { openai: { itemId: "msg_1" } } },
-        { type: "text-delta", id: "msg_1", text: "!", providerMetadata: { openai: { itemId: "msg_1" } } },
+        { type: "text-delta", id: "msg_1", text: "Hello" },
+        { type: "text-delta", id: "msg_1", text: "!" },
         {
           type: "request-finish",
           reason: "stop",
@@ -394,14 +394,12 @@ describe("OpenAI Responses route", () => {
           id: "call_1",
           name: "lookup",
           text: '{"query"',
-          providerMetadata: { openai: { itemId: "item_1" } },
         },
         {
           type: "tool-input-delta",
           id: "call_1",
           name: "lookup",
           text: ':"weather"}',
-          providerMetadata: { openai: { itemId: "item_1" } },
         },
         {
           type: "tool-call",