topology: add bcachefs-2copy; add bcachefs-single; rename single->btrfs-single; update planner, fs mapping, CLI, defaults, preview topo strings, README

README.md

@@ -24,7 +24,7 @@ Key modules
   - [src/mount/ops.rs](src/mount/ops.rs)
 
 Features at a glance
-- Topology-driven planning with built-in defaults: Single, DualIndependent, BtrfsRaid1, SsdHddBcachefs
+- Topology-driven planning with built-in defaults: BtrfsSingle, BcachefsSingle, DualIndependent, Bcachefs2Copy, BtrfsRaid1, SsdHddBcachefs
 - Non-destructive preview: --show/--report outputs JSON summary (disks, partition plan, filesystems, planned mountpoints)
 - Safe discovery: excludes removable media by default (USB sticks) unless explicitly allowed
 - Config-optional: the tool runs without any YAML; sensible defaults are always present and may be overridden/merged by config
@@ -45,7 +45,7 @@ Binary is target/release/zosstorage.
 
 CLI usage
 - Topology selection (config optional):
-  -t, --topology single|dual-independent|btrfs-raid1|ssd-hdd-bcachefs
+  -t, --topology btrfs-single|bcachefs-single|dual-independent|bcachefs-2copy|btrfs-raid1|ssd-hdd-bcachefs
 - Preview (non-destructive):
   --show                      Print JSON summary to stdout
   --report PATH               Write JSON summary to a file
@@ -61,7 +61,7 @@ CLI usage
 
 Examples
 - Single disk plan with debug logs:
-  sudo ./zosstorage --show -t single -l debug
+  sudo ./zosstorage --show -t btrfs-single -l debug
 - RAID1 btrfs across two disks; print and write summary:
   sudo ./zosstorage --show --report /run/zosstorage/plan.json -t btrfs-raid1 -l debug -L
 - SSD+HDD bcachefs plan, include removable devices (for lab cases):