Add app-server v2 thread realtime API (#12715)

Add experimental `thread/realtime/*` v2 requests and notifications, then
route app-server realtime events through that thread-scoped surface with
integration coverage.

---------

Co-authored-by: Codex <noreply@openai.com>

codex-rs/app-server-protocol/schema/json/ClientRequest.json

@@ -2052,6 +2052,38 @@
       ],
       "type": "object"
     },
+    "ThreadRealtimeAudioChunk": {
+      "description": "EXPERIMENTAL - thread realtime audio chunk.",
+      "properties": {
+        "data": {
+          "type": "string"
+        },
+        "numChannels": {
+          "format": "uint16",
+          "minimum": 0.0,
+          "type": "integer"
+        },
+        "sampleRate": {
+          "format": "uint32",
+          "minimum": 0.0,
+          "type": "integer"
+        },
+        "samplesPerChannel": {
+          "format": "uint32",
+          "minimum": 0.0,
+          "type": [
+            "integer",
+            "null"
+          ]
+        }
+      },
+      "required": [
+        "data",
+        "numChannels",
+        "sampleRate"
+      ],
+      "type": "object"
+    },
     "ThreadResumeParams": {
       "description": "There are three ways to resume a thread: 1. By thread_id: load the thread from disk by thread_id and resume it. 2. By history: instantiate the thread from memory and resume it. 3. By path: load the thread from disk by path and resume it.\n\nThe precedence is: history > path > thread_id. If using history or path, the thread_id param will be ignored.\n\nPrefer using thread_id whenever possible.",
       "properties": {