Allow publishing plugins through share updates (#33908)

## What changed

- Accept `LISTED` discoverability in `plugin/share/updateTargets` and forward it to the remote plugin sharing API.
- Update the generated JSON schemas and TypeScript type with the new enum value.

## Testing

- Add an app-server integration test that publishes a workspace plugin and verifies the `LISTED` request and response.

GitOrigin-RevId: 978f4b94b318e772bf80347e58dd5b1d2819a653

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

@@ -345,6 +345,9 @@ pub enum PluginShareUpdateDiscoverability {
     #[serde(rename = "PRIVATE")]
     #[ts(rename = "PRIVATE")]
     Private,
+    #[serde(rename = "LISTED")]
+    #[ts(rename = "LISTED")]
+    Listed,
 }
 
 #[derive(Serialize, Deserialize, Debug, Clone, Copy, PartialEq, Eq, JsonSchema, TS)]