fix(lint): restore clippy cleanliness after async ripple from std::fs work

Two follow-ups the workspace lint now catches:

- fabro-server tests/it/api/install.rs: a newer install-router integration
  test was missing the `.await` after `build_install_router(...)` -- the
  fn became async when the devcontainer/install-mode resolver was
  converted to tokio::fs in commit 19939c5f0.
- fabro-cli main.rs: add #[expect(clippy::disallowed_methods)] to the
  #[cfg(test)] module whose write_test_settings helper uses sync
  std::fs::write to stage CLI settings fixtures.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lib/crates/fabro-cli/src/main.rs

@@ -493,6 +493,10 @@ fn server_config_log_level(settings: &SettingsLayer) -> Option<String> {
 }
 
 #[cfg(test)]
+#[expect(
+    clippy::disallowed_methods,
+    reason = "main.rs tests stage CLI settings fixtures with sync std::fs::write"
+)]
 mod tests {
     use args::{
         Commands, InstallGitHubStrategyArg, ModelsCommand, ProviderCommand, ProviderNamespace,

lib/crates/fabro-server/tests/it/api/install.rs

@@ -416,7 +416,8 @@ async fn app_install_finish_omits_dev_token_and_does_not_write_it() {
         InstallAppState::for_test_with_paths("test-install-token", temp_dir.path(), &config_path)
             .with_home(home.clone())
             .with_github_api_base_url(github_mock.url("")),
-    );
+    )
+    .await;
 
     let llm_response = app
         .clone()