chore: plugin/uninstall endpoint (#14111)

add `plugin/uninstall` app-server endpoint to fully rm plugin from
plugins cache dir and rm entry from user config file.

plugin-enablement is session-scoped, so uninstalls are only picked up in
new sessions (like installs).

added tests.

codex-rs/app-server/tests/suite/v2/plugin_uninstall.rs

@@ -0,0 +1,84 @@
+use std::time::Duration;
+
+use anyhow::Result;
+use app_test_support::McpProcess;
+use app_test_support::to_response;
+use codex_app_server_protocol::JSONRPCResponse;
+use codex_app_server_protocol::PluginUninstallParams;
+use codex_app_server_protocol::PluginUninstallResponse;
+use codex_app_server_protocol::RequestId;
+use pretty_assertions::assert_eq;
+use tempfile::TempDir;
+use tokio::time::timeout;
+
+const DEFAULT_TIMEOUT: Duration = Duration::from_secs(10);
+
+#[tokio::test]
+async fn plugin_uninstall_removes_plugin_cache_and_config_entry() -> Result<()> {
+    let codex_home = TempDir::new()?;
+    write_installed_plugin(&codex_home, "debug", "sample-plugin")?;
+    std::fs::write(
+        codex_home.path().join("config.toml"),
+        r#"[features]
+plugins = true
+
+[plugins."sample-plugin@debug"]
+enabled = true
+"#,
+    )?;
+
+    let mut mcp = McpProcess::new(codex_home.path()).await?;
+    timeout(DEFAULT_TIMEOUT, mcp.initialize()).await??;
+
+    let params = PluginUninstallParams {
+        plugin_id: "sample-plugin@debug".to_string(),
+    };
+
+    let request_id = mcp.send_plugin_uninstall_request(params.clone()).await?;
+    let response: JSONRPCResponse = timeout(
+        DEFAULT_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(request_id)),
+    )
+    .await??;
+    let response: PluginUninstallResponse = to_response(response)?;
+    assert_eq!(response, PluginUninstallResponse {});
+
+    assert!(
+        !codex_home
+            .path()
+            .join("plugins/cache/debug/sample-plugin")
+            .exists()
+    );
+    let config = std::fs::read_to_string(codex_home.path().join("config.toml"))?;
+    assert!(!config.contains(r#"[plugins."sample-plugin@debug"]"#));
+
+    let request_id = mcp.send_plugin_uninstall_request(params).await?;
+    let response: JSONRPCResponse = timeout(
+        DEFAULT_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(request_id)),
+    )
+    .await??;
+    let response: PluginUninstallResponse = to_response(response)?;
+    assert_eq!(response, PluginUninstallResponse {});
+
+    Ok(())
+}
+
+fn write_installed_plugin(
+    codex_home: &TempDir,
+    marketplace_name: &str,
+    plugin_name: &str,
+) -> Result<()> {
+    let plugin_root = codex_home
+        .path()
+        .join("plugins/cache")
+        .join(marketplace_name)
+        .join(plugin_name)
+        .join("local/.codex-plugin");
+    std::fs::create_dir_all(&plugin_root)?;
+    std::fs::write(
+        plugin_root.join("plugin.json"),
+        format!(r#"{{"name":"{plugin_name}"}}"#),
+    )?;
+    Ok(())
+}