fix(scripts): add missing exit after error handlers

Critical bugs where error paths print a message but don't stop execution:
- install-fonts.sh: cd failure now exits properly
- install-ntfy.sh: unsupported OS case now exits with error
- install-git-crypt.sh: git clone and cd failures now exit properly

scripts/install-git-crypt.sh

@@ -19,8 +19,8 @@ if ! command -v git-crypt &> /dev/null; then
   rm -rf "$BUILD_PATH"
 
   if [ ! -d "$CHECK_PATH" ]; then
-    git clone --depth 1 "$REPO_URL" "$BUILD_PATH" || true
-    cd "$BUILD_PATH" || msg_err "$BUILD_PATH not found"
+    git clone --depth 1 "$REPO_URL" "$BUILD_PATH" || { msgr err "Failed to clone $REPO_URL"; exit 1; }
+    cd "$BUILD_PATH" || { msgr err "$BUILD_PATH not found"; exit 1; }
     make && make install PREFIX="$HOME/.local"
   else
     msgr run_done "git-crypt ($CHECK_PATH) already installed"