Add app-server remote browser bridge

Add an experimental browserSession command/notification pair, post commands to a configurable remote browser HTTP endpoint, and emit browser state updates back to clients.

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

codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.v2.schemas.json

@@ -715,6 +715,64 @@
         }
       ]
     },
+    "BrowserSessionState": {
+      "properties": {
+        "selectedTabId": {
+          "type": "string"
+        },
+        "tabs": {
+          "items": {
+            "$ref": "#/definitions/BrowserTabState"
+          },
+          "type": "array"
+        }
+      },
+      "required": [
+        "selectedTabId",
+        "tabs"
+      ],
+      "type": "object"
+    },
+    "BrowserSessionUpdatedNotification": {
+      "$schema": "http://json-schema.org/draft-07/schema#",
+      "properties": {
+        "browserSessionId": {
+          "type": "string"
+        },
+        "browserState": {
+          "$ref": "#/definitions/BrowserSessionState"
+        }
+      },
+      "required": [
+        "browserSessionId",
+        "browserState"
+      ],
+      "title": "BrowserSessionUpdatedNotification",
+      "type": "object"
+    },
+    "BrowserTabState": {
+      "properties": {
+        "id": {
+          "type": "string"
+        },
+        "selected": {
+          "type": "boolean"
+        },
+        "title": {
+          "type": "string"
+        },
+        "url": {
+          "type": "string"
+        }
+      },
+      "required": [
+        "id",
+        "selected",
+        "title",
+        "url"
+      ],
+      "type": "object"
+    },
     "ByteRange": {
       "properties": {
         "end": {
@@ -8518,6 +8576,26 @@
           "title": "App/list/updatedNotification",
           "type": "object"
         },
+        {
+          "properties": {
+            "method": {
+              "enum": [
+                "browserSession/updated"
+              ],
+              "title": "BrowserSession/updatedNotificationMethod",
+              "type": "string"
+            },
+            "params": {
+              "$ref": "#/definitions/BrowserSessionUpdatedNotification"
+            }
+          },
+          "required": [
+            "method",
+            "params"
+          ],
+          "title": "BrowserSession/updatedNotification",
+          "type": "object"
+        },
         {
           "properties": {
             "method": {