ci(e2e-autotest): add Linux to the runner matrix

The e2e-test job was hard-coded to `runs-on: windows-latest` even though
the autotest framework and the platformMap in this workflow were already
written to be OS-aware. This change wires the matrix axis through so we
exercise every plan on both Windows and Linux on every PR / schedule run.

Changes:
* matrix.os = [windows-latest, ubuntu-latest]; runs-on uses it
* JDK 25 step is now cross-platform pwsh (junction on Windows,
  symlink to /opt/jdk-25 on Linux, plus an in-place rewrite of the
  Windows-style java.jdt.ls.java.home in the java25 plan)
* New `Setup virtual display (Linux)` step installs xvfb and
  exports DISPLAY=:99 before the autotest CLI launches VS Code
  (the autotest framework does not spawn Xvfb itself)
* Artifact name suffix: results-<plan>-<os> so Windows and Linux
  results don't collide
* analyze.organize-results: preserve the <plan>-<os> suffix so the
  aggregate report keeps Windows and Linux runs distinct

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: wenytang-ms

.github/workflows/e2e-autotest.yml

@@ -88,11 +88,12 @@ jobs:
     needs: [discover, build-pack]
     # build-pack is skipped on schedule/workflow_dispatch — only require it on PRs
     if: ${{ always() && needs.discover.result == 'success' && (github.event_name != 'pull_request' || needs.build-pack.result == 'success') }}
-    runs-on: windows-latest
+    runs-on: ${{ matrix.os }}
     timeout-minutes: 30
     strategy:
       fail-fast: false
       matrix:
+        os: [windows-latest, ubuntu-latest]
         plan: ${{ fromJson(needs.discover.outputs.matrix) }}
 
     steps:
@@ -117,11 +118,24 @@ jobs:
           distribution: temurin
           java-version: 25-ea
 
-      - name: Create JDK 25 path
+      - name: Configure JDK 25 path for runner OS
         if: contains(matrix.plan, 'java25')
         shell: pwsh
         run: |
-          New-Item -ItemType Junction -Path "C:\Program Files\Java\jdk-25" -Target $env:JAVA_HOME
+          $planFile = "test-plans/${{ matrix.plan }}.yaml"
+          if ($IsWindows) {
+            $target = "C:\Program Files\Java\jdk-25"
+            New-Item -ItemType Junction -Path $target -Target $env:JAVA_HOME -Force | Out-Null
+            Write-Host "Created junction: $target -> $env:JAVA_HOME"
+          } else {
+            $target = "/opt/jdk-25"
+            sudo ln -sfn $env:JAVA_HOME $target
+            Write-Host "Created symlink: $target -> $env:JAVA_HOME"
+            # Linux: rewrite the Windows-style java.home setting in the plan
+            # so the language server resolves JDK 25 on this runner.
+            (Get-Content $planFile -Raw) -replace 'C:\\\\Program Files\\\\Java\\\\jdk-25', $target | Set-Content $planFile
+            Write-Host "Patched $planFile java.jdt.ls.java.home -> $target"
+          }
 
       - name: Setup Java 21
         uses: actions/setup-java@v4
@@ -132,6 +146,17 @@ jobs:
       - name: Install autotest CLI
         run: npm install -g @vscjava/vscode-autotest
 
+      - name: Setup virtual display (Linux)
+        if: runner.os == 'Linux'
+        shell: bash
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y xvfb
+          Xvfb :99 -screen 0 1920x1080x24 &
+          echo "DISPLAY=:99" >> "$GITHUB_ENV"
+          # Give Xvfb a moment to start before the autotest CLI launches VS Code.
+          sleep 2
+
       - name: Download PR VSIX (vscode-java-pack from branch)
         if: ${{ github.event_name == 'pull_request' }}
         uses: actions/download-artifact@v4
@@ -217,7 +242,7 @@ jobs:
         if: always()
         uses: actions/upload-artifact@v4
         with:
-          name: results-${{ matrix.plan }}
+          name: results-${{ matrix.plan }}-${{ matrix.os }}
           path: test-results/
           retention-days: 30
 
@@ -246,10 +271,13 @@ jobs:
       - name: Organize results
         run: |
           mkdir -p test-results
+          # Each artifact is named results-<plan>-<os>; keep that suffix so
+          # Windows and Linux runs of the same plan don't collide.
           for dir in all-results/results-*/; do
+            artifact=$(basename "$dir")          # results-<plan>-<os>
+            suffix="${artifact#results-}"        # <plan>-<os>
             find "$dir" -name "results.json" -exec dirname {} \; | while read d; do
-              name=$(basename "$d")
-              cp -r "$d" "test-results/$name"
+              cp -r "$d" "test-results/$suffix"
             done
           done
           echo "Organized results:"