fix(scanner): make distributed usage convergence authoritative (#5151)

* fix(scanner): make distributed usage cycles authoritative

* fix(scanner): close distributed refresh races

* fix(config): align scanner reload integration

* fix(admin): scope config test helpers

* fix(scanner): harden distributed usage convergence

* fix(scanner): preserve rolling activity compatibility

* fix(admin): expose non-secret optional config values

* fix(scanner): acknowledge distributed dirty usage

* fix(ecstore): make bucket mutations cancellation safe

* fix(scanner): preserve pending dirty acknowledgements

* test(obs): account for superseded scanner metric

* fix(api): reject excess detached bucket mutations

* test: close scanner convergence coverage gaps

* fix(scanner): make path tracking cleanup one-shot

---------

Co-authored-by: Henry Guo <marshawcoco@users.noreply.github.com>
Co-authored-by: houseme <housemecn@gmail.com>

crates/scanner/src/error.rs

@@ -36,7 +36,23 @@ pub enum ScannerError {
     #[error("Scanner error: {0}")]
     Other(String),
 
+    /// A remote namespace scanner request ID was already accepted.
+    #[error("Remote namespace scanner request replay detected")]
+    RemoteRequestReplay,
+
+    /// The bounded remote namespace scanner replay cache cannot accept more IDs yet.
+    #[error("Remote namespace scanner replay cache capacity exceeded")]
+    RemoteReplayCapacity,
+
+    /// A remote namespace scanner request is already active for the target disk.
+    #[error("Remote namespace scanner disk is already active")]
+    RemoteDiskBusy,
+
     /// Partial data usage cache produced before the scanner stopped.
     #[error("Scanner stopped with partial data usage cache")]
     PartialCache(Box<DataUsageCache>),
+
+    /// Partial cache retained because the bucket or scan root disappeared.
+    #[error("Scanner namespace path disappeared during the scan")]
+    NamespaceNotFoundCache(Box<DataUsageCache>),
 }