fix: handle directory entries in install — rm -rf, ln -sfn

scripts/dotfiles_manager.sh

@@ -385,12 +385,13 @@ cmd_install() {
             continue
         fi
 
-        # Back up conflicting file
+        # Back up conflicting file/directory
         if [ -e "$dest" ] && [ ! -L "$dest" ]; then
             mkdir -p "$BACKUP_DIR/$(dirname "$rel")"
             cp -a "$dest" "$BACKUP_DIR/$rel"
             warn "Backed up existing $dest"
-            rm -f "$dest"
+            # rm -rf needed when $dest is a real directory (e.g. ~/.bashrc.d created manually)
+            if [ -d "$dest" ]; then rm -rf "$dest"; else rm -f "$dest"; fi
         elif [ -L "$dest" ]; then
             rm "$dest"
         fi
@@ -404,7 +405,8 @@ cmd_install() {
             fi
         fi
 
-        ln -sf "$src" "$dest"
+        # -n: treat dest as a file (don't place link inside) if dest is a dir symlink
+        ln -sfn "$src" "$dest"
         success "Linked: ~/$rel → $src"
         (( count++ )) || true
     done < "$MANIFEST"
@@ -968,12 +970,12 @@ while IFS= read -r rel || [ -n "\$rel" ]; do
         mkdir -p "\$BACKUP_DIR/\$(dirname "\$rel")"
         cp -a "\$dest" "\$BACKUP_DIR/\$rel"
         echo "  Backed up: \$dest"
-        rm -f "\$dest"
+        if [ -d "\$dest" ]; then rm -rf "\$dest"; else rm -f "\$dest"; fi
     elif [ -L "\$dest" ]; then
         rm "\$dest"
     fi
     [[ "\$rel" == .ssh/* ]] && chmod 600 "\$src" 2>/dev/null || true
-    ln -sf "\$src" "\$dest"
+    ln -sfn "\$src" "\$dest"
     echo "  Linked: ~/\$rel"
 done < "\$MANIFEST"