chore: converge stale TODOs and apply safe fills (backlog#646) (#4322)

Second TODO-convergence round over the current tree (backlog#646). All
line numbers in the old inventory had gone stale after the set_disk /
diagnostics / cluster refactors, so this re-scans and reduces the marker
count from 144 to 99.

STALE removals (comment describes already-implemented behavior, or dead
commented-out blocks) across ecstore (set_disk ops/core, store,
cluster/rpc, bucket/metadata_sys, services), iam, filemeta, s3select and
rustfs auth/object_usecase. No behavior change.

Safe fills, each verified:
- filemeta: replication_info_equals now also compares
  replication_state_internal (function currently has no callers; adds a
  regression test).
- bitrot: drop the confirmed-unused `_want` parameter from bitrot_verify
  and the now-unused `sum` on LocalDisk::bitrot_verify, removing a
  Bytes::copy_from_slice allocation. Streaming verify uses the file's
  embedded per-shard hash, never the passed sum.
- signer: rename v4_ignored_headers -> V4_IGNORED_HEADERS and drop the
  non_upper_case_globals allow.
- admin/heal: test_decode was #[ignore]d and used serde_urlencoded on a
  JSON body (would panic); rewire to serde_json::from_slice to match the
  production decode path, add assertions, un-ignore.

Verified: cargo fmt; cargo check on touched crates; tests pass
(filemeta, signer, bitrot, heal::test_decode); arch guardrail scripts
pass.

crates/ecstore/src/core/sets.rs

@@ -176,7 +176,6 @@ impl Sets {
 
         let sets = Arc::new(Self {
             id: fm.id,
-            // sets: todo!(),
             disk_set,
             pool_idx,
             endpoints: endpoints.clone(),
@@ -194,10 +193,6 @@ impl Sets {
         let rx1 = rx.resubscribe();
         tokio::spawn(async move { asets.monitor_and_connect_endpoints(rx1).await });
 
-        // let sets2 = sets.clone();
-        // let rx2 = rx.resubscribe();
-        // tokio::spawn(async move { sets2.cleanup_deleted_objects_loop(rx2).await });
-
         Ok(sets)
     }
 
@@ -205,36 +200,6 @@ impl Sets {
         self.set_drive_count
     }
 
-    // pub async fn cleanup_deleted_objects_loop(self: Arc<Self>, mut rx: Receiver<()>) {
-    //     tokio::time::sleep(Duration::from_secs(5)).await;
-
-    //     info!("start cleanup_deleted_objects_loop");
-
-    //     // TODO: config interval
-    //     let mut interval = tokio::time::interval(Duration::from_secs(15 * 3));
-    //     loop {
-    //         tokio::select! {
-    //            _= interval.tick()=>{
-
-    //             info!("cleanup_deleted_objects_loop tick");
-
-    //             for set in self.disk_set.iter() {
-    //                 set.clone().cleanup_deleted_objects().await;
-    //             }
-
-    //             interval.reset();
-    //            },
-
-    //            _ = rx.recv() => {
-    //             warn!("cleanup_deleted_objects_loop ctx cancelled");
-    //             break;
-    //            }
-    //         }
-    //     }
-
-    //     warn!("cleanup_deleted_objects_loop exit");
-    // }
-
     pub async fn monitor_and_connect_endpoints(&self, mut rx: Receiver<()>) {
         tokio::time::sleep(Duration::from_secs(5)).await;
 
@@ -327,17 +292,6 @@ impl Sets {
         }
     }
 
-    // async fn commit_rename_data_dir(
-    //     &self,
-    //     disks: &Vec<Option<DiskStore>>,
-    //     bucket: &str,
-    //     object: &str,
-    //     data_dir: &str,
-    //     // write_quorum: usize,
-    // ) -> Vec<Option<Error>> {
-    //     unimplemented!()
-    // }
-
     async fn delete_prefix(&self, bucket: &str, object: &str, opts: &ObjectOptions) -> Result<()> {
         let mut futures = Vec::new();
         let mut opt = opts.clone();