Standardize 2-copy bcachefs topology naming to 'bcachefs-2copy' across code and docs; align parser and Display; update docs and ADR

src/types.rs

@@ -65,11 +65,9 @@ pub enum Topology {
     #[value(alias = "ssd-hdd-bcachefs")]
     SsdHddBcachefs,
     /// Multi-device bcachefs with two replicas (data+metadata).
-    #[value(
-        alias = "bcachefs2-copy",
-        alias = "bcachefs-2copy",
-        alias = "bcachefs-2-copy"
-    )]
+    /// Canonical token: bcachefs-2copy
+    #[serde(rename = "bcachefs-2copy")]
+    #[value(alias = "bcachefs-2copy")]
     Bcachefs2Copy,
     /// Optional mirrored btrfs across two disks when explicitly requested.
     #[value(alias = "btrfs-raid1")]
@@ -83,7 +81,8 @@ impl std::fmt::Display for Topology {
             Topology::BcachefsSingle => "bcachefs_single",
             Topology::DualIndependent => "dual_independent",
             Topology::SsdHddBcachefs => "ssd_hdd_bcachefs",
-            Topology::Bcachefs2Copy => "bcachefs2_copy",
+            // Canonical single notation for two-copy bcachefs topology
+            Topology::Bcachefs2Copy => "bcachefs-2copy",
             Topology::BtrfsRaid1 => "btrfs_raid1",
         };
         f.write_str(s)