gwen: Bundle pdfium in macOS builds

script/bundle-mac now downloads the pinned pdfium-mac tarball from
bblanchon/pdfium-binaries into Zed.app/Contents/Frameworks, matching
what bundle-linux and bundle-windows.ps1 already do, so the bundled
pdf_viewer no longer falls back to synthetic rendering on macOS. The
runtime loader probes ../Frameworks next to the executable.

crates/pdf_viewer/src/pdfium.rs

@@ -174,6 +174,13 @@ impl PdfiumEngine {
             PathBuf::from("/usr/local/lib/libpdfium.dylib"),
         ]);
 
+        // macOS app bundles ship libpdfium.dylib in Contents/Frameworks.
+        if let Ok(executable_path) = std::env::current_exe() {
+            if let Some(executable_dir) = executable_path.parent() {
+                common_paths.push(executable_dir.join("../Frameworks/libpdfium.dylib"));
+            }
+        }
+
         for path in &common_paths {
             if path.exists() {
                 if let Ok(bindings) = Pdfium::bind_to_library(path) {

script/bundle-mac

@@ -146,6 +146,7 @@ fi
 
 GIT_VERSION="v2.43.3"
 GIT_VERSION_SHA="fa29823"
+PDFIUM_TAG="chromium/8066"
 
 function download_and_unpack() {
     local url=$1
@@ -192,6 +193,42 @@ function download_git() {
     rm -rf "$tmp_dir"
 }
 
+function download_pdfium() {
+    local architecture=$1
+    local target_path=$2
+
+    case "$architecture" in
+        aarch64-apple-darwin)
+            pdfium_flavor="mac-arm64"
+            pdfium_sha256="336219e80580b93c6523f44db7dc1de59cc497b13a7390ddac84223f68ca162b"
+            ;;
+        x86_64-apple-darwin)
+            pdfium_flavor="mac-x64"
+            pdfium_sha256="841ecac278cdd46288dd065873522cf72f3996560d8978f473d336f01d59942c"
+            ;;
+        *)
+            echo "Unsupported architecture for pdfium: $architecture"
+            exit 1
+            ;;
+    esac
+
+    # sha256sum is not present on stock macOS, so checksums go through shasum.
+    pdfium_tgz="${target_dir}/pdfium-${pdfium_flavor}.tgz"
+    if ! echo "${pdfium_sha256}  ${pdfium_tgz}" | shasum -a 256 -c >/dev/null 2>&1; then
+        mkdir -p "${target_dir}"
+        curl --silent --fail --location --output "${pdfium_tgz}" \
+            "https://github.com/bblanchon/pdfium-binaries/releases/download/${PDFIUM_TAG}/pdfium-${pdfium_flavor}.tgz"
+        echo "${pdfium_sha256}  ${pdfium_tgz}" | shasum -a 256 -c
+    fi
+
+    pdfium_tmp=$(mktemp -d)
+    tar -xzf "${pdfium_tgz}" -C "${pdfium_tmp}" "lib/libpdfium.dylib" "LICENSE" "licenses"
+    cp "${pdfium_tmp}/lib/libpdfium.dylib" "${target_path}"
+    mkdir -p "${app_path}/Contents/Resources/pdfium-licenses"
+    cp "${pdfium_tmp}/LICENSE" "${pdfium_tmp}/licenses/"* "${app_path}/Contents/Resources/pdfium-licenses/"
+    rm -rf "${pdfium_tmp}"
+}
+
 function sign_app_binaries() {
     rm -rf "${app_path}/Contents/Frameworks"
     mkdir -p "${app_path}/Contents/Frameworks"
@@ -199,6 +236,10 @@ function sign_app_binaries() {
     echo "Downloading git binary"
     download_git "${target_triple}" "${app_path}/Contents/MacOS/git"
 
+    # PDFium is dlopen'd at runtime by the bundled pdf_viewer for native PDF viewing.
+    echo "Downloading pdfium library"
+    download_pdfium "${target_triple}" "${app_path}/Contents/Frameworks/libpdfium.dylib"
+
     # Note: The app identifier for our development builds is the same as the app identifier for nightly.
     cp crates/zed/contents/$channel/embedded.provisionprofile "${app_path}/Contents/"