fix(felhom-wipe): remove empty bind mount point dirs after nuclear wipe

After unmounting /mnt/hdd_1 (bind) and /mnt/.felhom-raw/hdd_1 (raw),
the /mnt/hdd_1 directory remained as an empty directory. Now rmdir is
called on each bind target after unmounting so the mount point is fully
cleaned up. rmdir (not rm -rf) ensures we only remove truly empty dirs.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/felhom-wipe.sh

@@ -258,7 +258,7 @@ print_plan() {
                 local bind_target
                 bind_target=$(grep -E "^/mnt/\.felhom-raw/${label}/" /etc/fstab 2>/dev/null | awk '{print $2}' | head -1 || true)
                 if [ -n "$bind_target" ]; then
-                    echo -e "    ${RED}umount${NC} ${bind_target} (bind) → ${rmp} (raw)"
+                    echo -e "    ${RED}umount + rmdir${NC} ${bind_target} (bind) → ${rmp} (raw)"
                 else
                     echo -e "    ${RED}umount${NC} ${rmp} (raw, no bind found)"
                 fi
@@ -311,8 +311,9 @@ cleanup_raw_mounts() {
     info "Cleaning up raw helper mounts (/mnt/.felhom-raw/)..."
 
     # 1. Unmount bind mounts whose source is inside .felhom-raw (field 1 matches)
+    #    Collect targets first so we can rmdir them after unmounting.
+    local bind_targets=""
     if [ -f /etc/fstab ]; then
-        local bind_targets
         bind_targets=$(grep -E '^/mnt/\.felhom-raw/' /etc/fstab | awk '{print $2}' || true)
         for mp in $bind_targets; do
             if mountpoint -q "$mp" 2>/dev/null; then
@@ -336,8 +337,17 @@ cleanup_raw_mounts() {
         sed -i '\|\.felhom-raw|d' /etc/fstab && info "  Removed .felhom-raw entries from /etc/fstab"
     fi
 
-    # 4. Remove directory — safe now that mounts are gone
+    # 4. Remove /mnt/.felhom-raw/ — safe now that mounts are gone
     rm -rf /mnt/.felhom-raw && info "  Removed: /mnt/.felhom-raw/"
+
+    # 5. Remove the now-empty bind target directories (e.g. /mnt/hdd_1).
+    #    Use rmdir so we only remove them if truly empty — never touch user data.
+    for mp in $bind_targets; do
+        if [ -d "$mp" ]; then
+            rmdir "$mp" 2>/dev/null && info "  Removed mount point: $mp" \
+                || warn "  Could not remove (not empty?): $mp"
+        fi
+    done
 }
 
 # --- Wipe Functions ---