chore(build): add support for prebuilt frontend assets in macOS and Windows build scripts

scripts/build-macos-universal.sh

@@ -15,7 +15,20 @@ export MESHCHATX_SKIP_BACKEND_MANIFEST=1
 
 pnpm run electron-postinstall
 pnpm run version:sync
-pnpm run build-frontend
+# Skip frontend rebuild when CI provides a prebuilt meshchatx/public artifact
+# via the reusable Frontend build workflow. Local invocations leave the flag
+# unset and continue to build everything from source.
+if [[ "${MESHCHATX_FRONTEND_PREBUILT:-0}" != "1" ]]; then
+    pnpm run build-frontend
+    pnpm run build-docs
+else
+    if [[ ! -f "meshchatx/public/index.html" ]]; then
+        echo "MESHCHATX_FRONTEND_PREBUILT=1 but meshchatx/public/index.html is missing." >&2
+        echo "Download the frontend artifact into meshchatx/public/ before invoking this script." >&2
+        exit 1
+    fi
+    echo "Reusing prebuilt frontend assets in meshchatx/public/."
+fi
 cross-env ARCH=arm64 pnpm run build-backend
 if [[ -n "${PYTHON_CMD_X64:-}" ]]; then
     cross-env ARCH=x64 PYTHON_CMD="$PYTHON_CMD_X64" pnpm run build-backend

scripts/ci/github-build-windows.sh

@@ -1,5 +1,10 @@
 #!/usr/bin/env bash
-# Build Windows portable + NSIS installers (electron-builder). See package.json dist:windows.
+# Build Windows portable + NSIS installers (electron-builder).
+#
+# When MESHCHATX_FRONTEND_PREBUILT=1 the script reuses the prebuilt
+# meshchatx/public/ artifact downloaded from the reusable Frontend build
+# workflow and only rebuilds the cx_Freeze backend. Otherwise it falls back to
+# the full pnpm dist:windows pipeline (frontend + docs + backend).
 set -euo pipefail
 
 ROOT="$(cd "$(dirname "$0")/../.." && pwd)"
@@ -7,4 +12,13 @@ cd "$ROOT"
 
 git config --global core.longpaths true 2>/dev/null || true
 
-pnpm run dist:windows
+if [[ "${MESHCHATX_FRONTEND_PREBUILT:-0}" == "1" ]]; then
+    if [[ ! -f "meshchatx/public/index.html" ]]; then
+        echo "MESHCHATX_FRONTEND_PREBUILT=1 but meshchatx/public/index.html is missing." >&2
+        echo "Download the frontend artifact into meshchatx/public/ before invoking this script." >&2
+        exit 1
+    fi
+    pnpm run dist:windows-prebuilt
+else
+    pnpm run dist:windows
+fi