fix: prevent .zshrc deletion during uninstall when no backup exists

Fixes #13156

- Enhanced uninstall script to automatically restore .zshrc from uninstall backup
  when no original backup (.zshrc.pre-oh-my-zsh) exists
- Improved install script to create backup even when KEEP_ZSHRC=yes
- Added better user feedback and error handling
- Prevents data loss for users who installed with --keep-zshrc option

The issue occurred when users installed oh-my-zsh with KEEP_ZSHRC=yes
(keeping their existing .zshrc), which didn't create a backup. During
uninstall, their .zshrc would be deleted with no backup to restore.

Now the uninstall process:
1. Creates a timestamped backup of current .zshrc
2. Looks for original backup (.zshrc.pre-oh-my-zsh)
3. If found, restores the original
4. If not found, automatically restores from the uninstall backup
5. Provides clear feedback to the user

This ensures users never lose their .zshrc configuration during uninstall.

tools/install.sh

@@ -341,6 +341,11 @@ setup_zshrc() {
     # Skip this if the user doesn't want to replace an existing .zshrc
     if [ "$KEEP_ZSHRC" = yes ]; then
       echo "${FMT_YELLOW}Found ${zdot}/.zshrc.${FMT_RESET} ${FMT_GREEN}Keeping...${FMT_RESET}"
+      # Still create a backup for uninstall safety, but don't overwrite the existing .zshrc
+      if [ ! -e "$OLD_ZSHRC" ]; then
+        echo "${FMT_GREEN}Creating backup at ${OLD_ZSHRC} for safe uninstall${FMT_RESET}"
+        cp "$zdot/.zshrc" "$OLD_ZSHRC"
+      fi
       return
     fi
     

tools/uninstall.sh

@@ -35,6 +35,19 @@ if [ -e "$ZSHRC_ORIG" ]; then
   echo "Your original zsh config was restored."
 else
   echo "No original zsh config found"
+  # Check if we have a backup from this uninstall session
+  if [ -e ~/.zshrc.omz-uninstalled-* ]; then
+    echo "However, your .zshrc was backed up during this uninstall."
+    echo "Restoring it automatically..."
+    # Find the most recent backup and restore it
+    LATEST_BACKUP=$(ls -t ~/.zshrc.omz-uninstalled-* 2>/dev/null | head -1)
+    if [ -n "$LATEST_BACKUP" ]; then
+      mv "$LATEST_BACKUP" ~/.zshrc
+      echo "Your .zshrc has been restored from backup."
+    fi
+  else
+    echo "No backup found. You may need to recreate your .zshrc configuration."
+  fi
 fi
 
 echo "Thanks for trying out Oh My Zsh. It's been uninstalled."