fix(clippy): restore workspace lint cleanups after main merge

Reapply the lint-safe changes that were partially displaced while merging
origin/main, including the billing serialization assertion and the attach
replay/server annotation cleanups. This keeps the merged main branch back to a
clean full-workspace clippy pass before the store-dump debugging continues.

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

@@ -5,10 +5,10 @@ pub(crate) use fabro_config::user::*;
 use anyhow::{Result, bail};
 use fabro_config::ConfigLayer;
 use fabro_types::Settings;
+use fabro_util::version::FABRO_VERSION;
 use tracing::debug;
 
 use crate::args::ServerTargetArgs;
-use fabro_util::version::FABRO_VERSION;
 
 pub(crate) fn load_settings() -> anyhow::Result<Settings> {
     load_settings_with_config_and_storage_dir(None, None)

lib/crates/fabro-llm/src/providers/anthropic.rs

@@ -162,8 +162,8 @@ struct ApiResponse {
     usage: ApiUsage,
 }
 
-#[allow(clippy::struct_field_names)]
 #[derive(serde::Deserialize)]
+#[allow(clippy::struct_field_names)] // Match Anthropic's API usage payload field names.
 struct ApiUsage {
     input_tokens: i64,
     output_tokens: i64,

lib/crates/fabro-model/src/billing.rs

@@ -247,7 +247,7 @@ pub struct ModelPricing {
     pub policy: ModelPricingPolicy,
 }
 
-#[allow(clippy::empty_structs_with_brackets)]
+#[allow(clippy::empty_structs_with_brackets)] // Serialize as `{}` rather than unit-struct `null`.
 #[derive(Debug, Clone, PartialEq, Eq, Default, Serialize, Deserialize)]
 pub struct OpenAiBillingFacts {}
 
@@ -735,4 +735,12 @@ mod tests {
 
         assert_eq!(price.usd_micros, i64::MAX);
     }
+
+    #[test]
+    fn openai_billing_facts_serialize_as_empty_object() {
+        assert_eq!(
+            serde_json::to_value(OpenAiBillingFacts::default()).unwrap(),
+            serde_json::json!({})
+        );
+    }
 }

lib/crates/fabro-server/src/serve.rs

@@ -472,7 +472,7 @@ async fn wait_for_shutdown(mut shutdown_rx: watch::Receiver<bool>) {
     let _ = shutdown_rx.changed().await;
 }
 
-#[allow(clippy::print_stderr)]
+#[allow(clippy::print_stderr)] // Startup status belongs on stderr for operator-facing CLI output.
 fn announce_server_ready(bind_addr: &Bind, styles: &'static Styles, dry_run_mode: bool) {
     set_server_title(ServerTitlePhase::Listening, Some(bind_addr));
     info!(bind = %bind_addr, dry_run = dry_run_mode, "API server started");

lib/crates/fabro-server/src/server.rs

@@ -110,8 +110,6 @@ pub fn default_page_limit() -> u32 {
     20
 }
 
-const ATTACH_REPLAY_BATCH_LIMIT: usize = 256;
-
 #[derive(serde::Deserialize)]
 pub struct PaginationParams {
     #[serde(rename = "page[limit]", default = "default_page_limit")]
@@ -2559,7 +2557,7 @@ fn api_question_from_interview_question(id: &str, question: &Question) -> ApiQue
     }
 }
 
-#[allow(clippy::result_large_err)]
+#[allow(clippy::result_large_err)] // Axum handlers naturally propagate full `Response` errors.
 fn answer_from_request(req: SubmitAnswerRequest, question: &Question) -> Result<Answer, Response> {
     if let Some(key) = req.selected_option_key {
         let option = question
@@ -3645,6 +3643,8 @@ async fn attach_run_events(
     Path(id): Path<String>,
     Query(params): Query<AttachParams>,
 ) -> Response {
+    const ATTACH_REPLAY_BATCH_LIMIT: usize = 256;
+
     let id = match parse_run_id_path(&id) {
         Ok(id) => id,
         Err(response) => return response,