Wire the PatchUpdated events through app_server (#18289)

Wires patch_updated events through app_server. These events are parsed
and streamed while apply_patch is being written by the model. Also adds 500ms of buffering to the patch_updated events in the diff_consumer.

The eventual goal is to use this to display better progress indicators in
the codex app.

codex-rs/app-server-protocol/src/protocol/common.rs

@@ -1023,6 +1023,7 @@ server_notification_definitions! {
     CommandExecutionOutputDelta => "item/commandExecution/outputDelta" (v2::CommandExecutionOutputDeltaNotification),
     TerminalInteraction => "item/commandExecution/terminalInteraction" (v2::TerminalInteractionNotification),
     FileChangeOutputDelta => "item/fileChange/outputDelta" (v2::FileChangeOutputDeltaNotification),
+    FileChangePatchUpdated => "item/fileChange/patchUpdated" (v2::FileChangePatchUpdatedNotification),
     ServerRequestResolved => "serverRequest/resolved" (v2::ServerRequestResolvedNotification),
     McpToolCallProgress => "item/mcpToolCall/progress" (v2::McpToolCallProgressNotification),
     McpServerOauthLoginCompleted => "mcpServer/oauthLogin/completed" (v2::McpServerOauthLoginCompletedNotification),

codex-rs/app-server-protocol/src/protocol/v2.rs

@@ -5935,6 +5935,16 @@ pub struct FileChangeOutputDeltaNotification {
     pub delta: String,
 }
 
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct FileChangePatchUpdatedNotification {
+    pub thread_id: String,
+    pub turn_id: String,
+    pub item_id: String,
+    pub changes: Vec<FileUpdateChange>,
+}
+
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
 #[serde(rename_all = "camelCase")]
 #[ts(export_to = "v2/")]