Bundle swift-testing helper dylibs in CI build products

Xcode 26.4 split swift-testing's interop logic out of Testing.framework
into a separate lib_TestingInterop.dylib that lives in
Platforms/<plat>/Developer/usr/lib. `xcodebuild build-for-testing`
embeds Testing.framework into the .app/Frameworks but leaves this
sibling dylib behind, so when the test stage runs on a machine whose
Xcode predates the split (e.g. macos-15 with Xcode 16.4), dyld can't
locate @rpath/lib_TestingInterop.dylib and the app aborts before any
test starts.

Copy every lib_*.dylib next to Testing.framework after the build to
restore the previous self-contained xctestproducts layout. Globbing
the lib_* prefix keeps the workaround forward-compatible if Apple
splits further helpers in later Xcodes.

Author: sinoru

.github/workflows/ci.yml

@@ -53,6 +53,45 @@ jobs:
           -testProductsPath '${{ runner.temp }}/PatronArchiver.xctestproducts'
           CODE_SIGNING_ALLOWED=NO
 
+      # WORKAROUND: Xcode 26.4+ split swift-testing's interop into a
+      # separate lib_TestingInterop.dylib, but `xcodebuild
+      # build-for-testing` only embeds Testing.framework itself in
+      # .app/Frameworks — the sibling dylib (in
+      # Platforms/.../Developer/usr/lib) is left out, so dyld aborts the
+      # app on test machines whose Xcode toolchain predates the split.
+      # Copy every lib_*.dylib sibling alongside the embedded
+      # Testing.framework so future splits are also covered.
+      - name: 'Workaround: Bundle swift-testing helper dylibs'
+        run: |
+          set -euo pipefail
+          XCT_PRODUCTS='${{ runner.temp }}/PatronArchiver.xctestproducts'
+          if [ '${{ matrix.platform }}' = 'macOS' ]; then
+            plat='MacOSX.platform'
+            cfg='Debug'
+            app_fw='PatronArchiver.app/Contents/Frameworks'
+            ui_fw='PatronArchiverUITests-Runner.app/Contents/Frameworks'
+          else
+            plat='iPhoneSimulator.platform'
+            cfg='Debug-iphonesimulator'
+            app_fw='PatronArchiver.app/Frameworks'
+            ui_fw='PatronArchiverUITests-Runner.app/Frameworks'
+          fi
+          src_dir="$(xcode-select -p)/Platforms/$plat/Developer/usr/lib"
+          dst_base="$XCT_PRODUCTS/Binaries/0/$cfg"
+
+          shopt -s nullglob
+          siblings=("$src_dir"/lib_*.dylib)
+          if [ ${#siblings[@]} -eq 0 ]; then
+            echo "::notice::No lib_*.dylib found in $src_dir; nothing to bundle"
+            exit 0
+          fi
+          for dst in "$dst_base/$app_fw" "$dst_base/$ui_fw"; do
+            [ -d "$dst" ] || continue
+            for dylib in "${siblings[@]}"; do
+              cp -v "$dylib" "$dst/"
+            done
+          done
+
       - name: Archive Test Products
         run: >
           ditto -c -k --sequesterRsrc --keepParent