Add macOS build helper script

Adds a root-level `build.sh` for configuring and building Nebula Browser with CMake on macOS, including clean and configure-only modes. Also removes an unused `Trim` helper from the extension manager.

build.sh

@@ -0,0 +1,71 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Build Nebula Browser (macOS).
+# Usage:
+#   ./build.sh              - configure + Release build
+#   ./build.sh Debug        - configure + Debug build
+#   ./build.sh Release      - configure + Release build
+#   ./build.sh configure    - configure only
+#   ./build.sh clean        - remove the build folder
+
+cd "$(dirname "$0")"
+
+if [[ "${1:-}" == "clean" ]]; then
+    echo "Removing build/ ..."
+    rm -rf build
+    echo "Done."
+    exit 0
+fi
+
+CONFIG="Release"
+case "${1:-}" in
+    Debug|debug) CONFIG="Debug" ;;
+    Release|release) CONFIG="Release" ;;
+esac
+
+if [[ ! -f "thirdparty/cef/cmake/FindCEF.cmake" ]]; then
+    echo "ERROR: CEF not found at thirdparty/cef/"
+    echo "Download a macOS CEF standard binary distribution and extract it"
+    echo "so that thirdparty/cef/cmake/FindCEF.cmake exists."
+    exit 1
+fi
+
+case "$(uname -m)" in
+    arm64) PROJECT_ARCH="arm64" ;;
+    x86_64) PROJECT_ARCH="x86_64" ;;
+    *)
+        echo "ERROR: Unsupported architecture: $(uname -m)"
+        exit 1
+        ;;
+esac
+
+echo "Configuring CMake (arch=$PROJECT_ARCH, config=$CONFIG)..."
+cmake -B build \
+    -DPROJECT_ARCH="$PROJECT_ARCH" \
+    -DCMAKE_BUILD_TYPE="$CONFIG" \
+    || { echo "Configure failed."; exit 1; }
+
+if [[ "${1:-}" == "configure" ]]; then
+    echo "Configure complete."
+    exit 0
+fi
+
+echo "Building $CONFIG..."
+cmake --build build --config "$CONFIG" \
+    || { echo "Build failed."; exit 1; }
+
+APP_PATH=""
+for candidate in "build/$CONFIG/NebulaBrowser.app" "build/NebulaBrowser.app"; do
+    if [[ -d "$candidate" ]]; then
+        APP_PATH="$candidate"
+        break
+    fi
+done
+
+echo ""
+if [[ -n "$APP_PATH" ]]; then
+    echo "Build succeeded: $APP_PATH"
+else
+    echo "Build succeeded (app bundle location may vary under build/)"
+fi