Keep a web app name out of the launcher's directory structure

The app name becomes a filename, and omarchy-webapp-install ran
`mkdir -p "$(dirname "$DESKTOP_FILE")"` over it, so every slash turned into a
directory level. Typing a URL into the Name field -- the reported way in --
wrote the launcher to
`~/.local/share/applications/http:/127.0.0.1:4000/.desktop`.

Removal could then never reach it. The picker lists the file but displays a
name derived from the path, and the removal rebuilt a flat
`$DESKTOP_DIR/$APP_NAME.desktop` from that name, so `rm -f` deleted nothing and
the app stayed in the launcher with no error.

Refuse a name containing a slash rather than silently renaming what the user
typed, and delete the file the scan actually found instead of a path rebuilt
from its display name. The second half also clears up whatever earlier versions
nested, which a reconstructed path cannot address.

bin/omarchy-webapp-install

@@ -104,6 +104,15 @@ if [[ -z $APP_NAME || -z $APP_URL ]]; then
   exit 1
 fi
 
+# The name becomes a filename. A slash would turn it into directory levels, so
+# the launcher lands somewhere omarchy-webapp-remove cannot address and the app
+# is stuck in the launcher. Refuse rather than silently renaming what the user
+# typed -- most often it is a URL entered in the name field.
+if [[ $APP_NAME == */* ]]; then
+  echo "App name cannot contain '/': $APP_NAME"
+  exit 1
+fi
+
 if [[ -z $ICON_REF ]]; then
   ICON_VALUE=$(safe_icon_name "$APP_NAME")
   mkdir -p "$ICON_DIR"
@@ -132,8 +141,9 @@ fi
 EXEC_COMMAND="${CUSTOM_EXEC:-omarchy-launch-webapp $APP_URL}"
 
 # Create application .desktop file
-DESKTOP_FILE="$HOME/.local/share/applications/$APP_NAME.desktop"
-mkdir -p "$(dirname "$DESKTOP_FILE")"
+DESKTOP_DIR="$HOME/.local/share/applications"
+DESKTOP_FILE="$DESKTOP_DIR/$APP_NAME.desktop"
+mkdir -p "$DESKTOP_DIR"
 
 cat >"$DESKTOP_FILE" <<EOF
 [Desktop Entry]