Add startup confirmation to disk utilities

lib/common.sh

@@ -54,6 +54,33 @@ common::log() {
     echo "[$(date '+%Y-%m-%d %H:%M:%S')] $*" >&2
 }
 
+# common::confirm returns success only when the user answers yes.
+# A no answer or end-of-input cancels the caller; invalid answers are retried.
+common::confirm() {
+    local prompt="$1"
+    local answer
+
+    while true; do
+        if ! read -r -p "${prompt} [yes/no]: " answer; then
+            common::log "No response received; cancelling."
+            return 1
+        fi
+
+        case "${answer,,}" in
+            yes)
+                return 0
+                ;;
+            no)
+                common::log "Cancelled by user."
+                return 1
+                ;;
+            *)
+                printf "Please answer 'yes' or 'no'.\n" >&2
+                ;;
+        esac
+    done
+}
+
 # common::require_cmd fails fast with a clear message if a required
 # external command is missing from PATH, instead of letting the script
 # fail later with a cryptic "command not found".