chore(app-server): add experimental annotation to relevant fields (#10928)

These fields had always been documented as experimental/unstable with
docstrings, but now let's actually use the `experimental` annotation to
be more explicit.

- thread/start.experimentalRawEvents
- thread/resume.history
- thread/resume.path
- thread/fork.path
- turn/start.collaborationMode
- account/login/start.chatgptAuthTokens

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

@@ -2323,13 +2323,6 @@
             "null"
           ]
         },
-        "path": {
-          "description": "[UNSTABLE] Specify the rollout path to fork from. If specified, the thread_id param will be ignored.",
-          "type": [
-            "string",
-            "null"
-          ]
-        },
         "sandbox": {
           "anyOf": [
             {
@@ -2486,16 +2479,6 @@
             "null"
           ]
         },
-        "history": {
-          "description": "[UNSTABLE] FOR CODEX CLOUD - DO NOT USE. If specified, the thread will be resumed with the provided history instead of loaded from disk.",
-          "items": {
-            "$ref": "#/definitions/ResponseItem"
-          },
-          "type": [
-            "array",
-            "null"
-          ]
-        },
         "model": {
           "description": "Configuration overrides for the resumed thread, if any.",
           "type": [
@@ -2509,13 +2492,6 @@
             "null"
           ]
         },
-        "path": {
-          "description": "[UNSTABLE] Specify the rollout path to resume from. If specified, the thread_id param will be ignored.",
-          "type": [
-            "string",
-            "null"
-          ]
-        },
         "personality": {
           "anyOf": [
             {
@@ -2643,11 +2619,6 @@
             "null"
           ]
         },
-        "experimentalRawEvents": {
-          "default": false,
-          "description": "If true, opt into emitting raw response items on the event stream.\n\nThis is for internal use only (e.g. Codex Cloud). (TODO): Figure out a better way to categorize internal / experimental events & protocols.",
-          "type": "boolean"
-        },
         "model": {
           "type": [
             "string",
@@ -2722,17 +2693,6 @@
           ],
           "description": "Override the approval policy for this turn and subsequent turns."
         },
-        "collaborationMode": {
-          "anyOf": [
-            {
-              "$ref": "#/definitions/CollaborationMode"
-            },
-            {
-              "type": "null"
-            }
-          ],
-          "description": "EXPERIMENTAL - set a pre-set collaboration mode. Takes precedence over model, reasoning_effort, and developer instructions if set."
-        },
         "cwd": {
           "description": "Override the working directory for this turn and subsequent turns.",
           "type": [