chore(ecstore): drop the bucket dead_code blanket (#6147)

* chore(ecstore): drop the bucket dead_code blanket

The last blanket of the backlog#1823 burn-down, and the largest: 71 items across lifecycle, replication, metadata, quota, object lock and bucket utils. Four are deleted.

Deleted, all trivial:

- check_valid_object_name and check_valid_object_name_prefix, a pair that only calls into each other with no external caller. Worth stating plainly so nobody reads this as a validation gap: object names are validated through check_object_name_for_length_and_slash, which is live; this pair is a second, unwired entry point.
- DEFAULT_HEALTH_CHECK_RELOAD_DURATION, a lone unused constant.
- The LifecycleReplicationConfig alias, which orphaned a re-export in replication/mod.rs that goes with it.

Everything else is kept, in four groups, because the blanket here was hiding structure rather than rot:

Windows platform gating. WINDOWS_RESERVED_NAMES, the two reason constants and object_name_has_windows_incompatible_segment are called from inside the #[cfg(target_os = "windows")] block in check_object_name_for_length_and_slash (utils.rs:228-255), so they only read as dead on non-Windows hosts. As with the Linux gating in the disk root, this cannot be adjudicated locally: cargo check for both x86_64-pc-windows-msvc and x86_64-unknown-linux-gnu fails in the aws-lc-sys build script for want of a cross C toolchain. CI covers both.

Declared boundary surface. The *_boundary.rs and *_bridge.rs files carry the replication split plan's contracts, which scripts/check_architecture_migration_rules.sh pins through the EcstoreReplicationBoundaryImports section of the split-plan doc. Their unused items are declarations, not leftovers.

test-util seams. ConfigWriteLockProbe with install/wait_until_attempted follows the same pattern as the barriers in the services and set_disk roots.

MinIO-parity tier/lifecycle entry points that this port never wired: apply_lifecycle_action, get_transitioned_object_reader, recover_tier_free_versions, delete_object_from_remote_tier, abort_tier_delete_journal_entry and the replication pool's worker-management surface. These are complete, substantial machinery with no caller — the same shape as data_usage's local_snapshot feature. Removing them is a product decision, so they are made explicit here rather than deleted.

Verification, four lanes warning-free: default, --tests, --features rio-v2 --tests, --features test-util --tests. cargo nextest run -p rustfs-ecstore 4096 passed; clippy --lib --tests -D warnings clean; make pre-commit exit 0. Note that clippy is what caught the orphaned re-export above: cargo check and pre-commit both treat unused_imports as a warning.

Ref rustfs/backlog#1823 (step 2, final root).

* chore(ecstore): correct inaccurate dead_code reasons in the bucket root

Six items were labelled 'asserted by this file's tests' or as MinIO-parity
entry points while having no caller at all - free get_bucket_acl_config and
created_at only reach their own live methods (production goes through
created_at_in), BucketVersioningSys::get_in, utils::serialize_content and
ServiceType have no reference anywhere, and with_transition_queue_env_async
is an unused test fixture, not a tier entry point. Name what each one is so
the next reader does not assume coverage that is not there.

Ref rustfs/backlog#1823.

crates/ecstore/src/bucket/replication/replication_pool.rs

@@ -217,6 +217,10 @@ impl DurableMrfBacklogTracker {
     }
 }
 
+#[allow(
+    dead_code,
+    reason = "MinIO-parity replication surface with no caller in this port (backlog#1823)"
+)]
 fn durable_mrf_backlog_tracker_from_entries(entries: &[MrfReplicateEntry]) -> DurableMrfBacklogTracker {
     let mut tracker = DurableMrfBacklogTracker {
         available: true,
@@ -712,6 +716,10 @@ pub struct ReplicationPool<S: ReplicationStorage> {
 
     // MRF worker lifecycle
     mrf_worker_cancellations: Mutex<Vec<CancellationToken>>,
+    #[allow(
+        dead_code,
+        reason = "MinIO-parity replication surface with no caller in this port (backlog#1823)"
+    )]
     mrf_stop_tx: Sender<()>,
 
     // Worker size tracking
@@ -940,6 +948,10 @@ impl<S: ReplicationStorage> ReplicationPool<S> {
     }
 
     /// Resizes worker priority and counts
+    #[allow(
+        dead_code,
+        reason = "MinIO-parity replication surface with no caller in this port (backlog#1823)"
+    )]
     pub async fn resize_worker_priority(
         &self,
         pri: ReplicationPriority,
@@ -1180,6 +1192,10 @@ impl<S: ReplicationStorage> ReplicationPool<S> {
     }
 
     /// Queues an MRF save operation
+    #[allow(
+        dead_code,
+        reason = "MinIO-parity replication surface with no caller in this port (backlog#1823)"
+    )]
     async fn queue_mrf_save(&self, entry: MrfReplicateEntry) {
         let _ = self.queue_mrf_save_admission(entry, "mrf_worker").await;
     }
@@ -1651,6 +1667,10 @@ impl<S: ReplicationStorage> ReplicationPool<S> {
     }
 
     /// Worker function for handling regular replication operations
+    #[allow(
+        dead_code,
+        reason = "MinIO-parity replication surface with no caller in this port (backlog#1823)"
+    )]
     async fn add_worker(
         &self,
         mut rx: Receiver<ReplicationOperation>,
@@ -1664,6 +1684,10 @@ impl<S: ReplicationStorage> ReplicationPool<S> {
     }
 
     /// Worker function for handling large object replication operations
+    #[allow(
+        dead_code,
+        reason = "MinIO-parity replication surface with no caller in this port (backlog#1823)"
+    )]
     async fn add_large_worker(
         &self,
         mut rx: Receiver<ReplicationOperation>,
@@ -1678,6 +1702,10 @@ impl<S: ReplicationStorage> ReplicationPool<S> {
     }
 
     /// Worker function for handling MRF (Most Recent Failures) operations
+    #[allow(
+        dead_code,
+        reason = "MinIO-parity replication surface with no caller in this port (backlog#1823)"
+    )]
     async fn add_mrf_worker(
         &self,
         mut rx: Receiver<ReplicationOperation>,
@@ -1691,6 +1719,10 @@ impl<S: ReplicationStorage> ReplicationPool<S> {
     }
 
     /// Delete resync metadata from replication resync state in memory
+    #[allow(
+        dead_code,
+        reason = "MinIO-parity replication surface with no caller in this port (backlog#1823)"
+    )]
     pub async fn delete_resync_metadata(&self, bucket: &str) {
         let mut status_map = self.resyncer.status_map.write().await;
         status_map.remove(bucket);