ci(e2e): run Playwright suite on macOS alongside Linux

macOS is the primary shipped platform but e2e only ran on Linux, so a
whole class of platform/path bugs went uncaught in CI. The afterPack
Linux-vs-macOS executable-name divergence is the canonical example:
mac uses productFilename, Linux uses executableName, and only running
the suite on both surfaces that kind of drift.

Add a fail-fast:false os matrix (ubuntu-latest, macos-latest). The
Linux-only steps stay gated so the ubuntu leg is byte-for-byte the same
work as before: the Electron-binary unzip workaround (linux-x64 zip,
dist/electron) and npx playwright install-deps are guarded with
if: matrix.os == 'ubuntu-latest', and xvfb-run wraps the suite only when
RUNNER_OS is Linux. macOS extracts dist/Electron.app via the normal
postinstall and has a real display, so it needs neither. The venv
provisioning and JLAB_TEST_PYTHON_PATH work unchanged on both. Artifacts
are named per-OS so the two legs do not clobber each other.

Note: AI-assisted (Claude Code). Manually verified: yaml parse (python yaml.safe_load) + that the ubuntu leg is unchanged (same steps, same commands, gates only add macOS); macOS leg verified by reading, not run (cannot run macOS CI locally).

Author: notluquis

.github/workflows/e2e.yml

@@ -15,8 +15,12 @@ concurrency:
 
 jobs:
   e2e:
-    name: 'Playwright (Linux)'
-    runs-on: ubuntu-latest
+    name: 'Playwright (${{ matrix.os }})'
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest]
+    runs-on: ${{ matrix.os }}
     # Bound the job so a stuck Electron launch/close fails fast instead of
     # tying up a runner; this suite specifically guards shutdown hangs.
     timeout-minutes: 15
@@ -37,8 +41,11 @@ jobs:
       # binary on this runner even though the downloaded zip is complete and
       # valid, so launch fails with "Electron failed to install correctly". Let
       # install.js fetch the zip into the cache, then extract it with the system
-      # `unzip` and point path.txt at the binary.
+      # `unzip` and point path.txt at the binary. Linux-only: the zip is the
+      # linux-x64 build and the binary lives at dist/electron. On macOS the
+      # postinstall extracts dist/Electron.app correctly and needs no workaround.
       - name: Install the Electron binary
+        if: matrix.os == 'ubuntu-latest'
         run: |
           set -euo pipefail
           node node_modules/electron/install.js || true
@@ -51,8 +58,10 @@ jobs:
       - run: yarn build
       # Electron needs system libraries; xvfb provides a display on the headless
       # runner. The app launches up to four windows, so a real display beats
-      # --headless here.
-      - run: npx playwright install-deps
+      # --headless here. Both are Linux-only: macOS runners have a display and do
+      # not use this apt-based dependency installer.
+      - if: matrix.os == 'ubuntu-latest'
+        run: npx playwright install-deps
       # A minimal Python env with jupyterlab so the env-backed tests run (a venv
       # + pip is lighter than a full conda env for a smoke). The seeded
       # app-data.json points the app at this interpreter.
@@ -67,11 +76,19 @@ jobs:
           python3 -m venv "$RUNNER_TEMP/jlab-venv"
           "$RUNNER_TEMP/jlab-venv/bin/pip" install --quiet "jupyterlab==$ver"
           echo "JLAB_TEST_PYTHON_PATH=$RUNNER_TEMP/jlab-venv/bin/python" >> "$GITHUB_ENV"
-      - run: xvfb-run -a yarn test:e2e
+      # xvfb is Linux-only; on macOS the runner has a real display, so run the
+      # suite directly. Same yarn test:e2e command on both legs.
+      - name: Run the e2e suite
+        run: |
+          if [ "$RUNNER_OS" = "Linux" ]; then
+            xvfb-run -a yarn test:e2e
+          else
+            yarn test:e2e
+          fi
       - uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4
         if: ${{ !cancelled() }}
         with:
-          name: playwright-report
+          name: playwright-report-${{ matrix.os }}
           path: |
             playwright-report/
             test-results/