ci(parakeet-cpp): wire transcription gRPC e2e test into test-extra

The L3 commit added the test-extra-backend-parakeet-cpp-transcription
Makefile target but never invoked it in CI. Mirror the whisper job:

- Add a parakeet-cpp output to detect-changes (emitted by
  changed-backends.js from the matrix entry).
- Add tests-parakeet-cpp-grpc-transcription, gated on the parakeet-cpp
  path filter / run-all, building the backend image and running the
  transcription e2e against tdt_ctc-110m + the JFK clip.

Assisted-by: Claude:claude-opus-4-8 [Claude Code]

.github/workflows/test-extra.yml

@@ -46,6 +46,7 @@ jobs:
       speaker-recognition: ${{ steps.detect.outputs.speaker-recognition }}
       sherpa-onnx: ${{ steps.detect.outputs.sherpa-onnx }}
       whisper: ${{ steps.detect.outputs.whisper }}
+      parakeet-cpp: ${{ steps.detect.outputs.parakeet-cpp }}
     steps:
       - name: Checkout repository
         uses: actions/checkout@v6
@@ -633,6 +634,26 @@ jobs:
       - name: Build whisper backend image and run transcription gRPC e2e tests
         run: |
           make test-extra-backend-whisper-transcription
+  # Parakeet ASR via the parakeet-cpp backend (C++/ggml port of NeMo
+  # Parakeet). Drives AudioTranscription (offline, with word timestamps) on
+  # tdt_ctc-110m + the JFK 11s clip.
+  tests-parakeet-cpp-grpc-transcription:
+    needs: detect-changes
+    if: needs.detect-changes.outputs.parakeet-cpp == 'true' || needs.detect-changes.outputs.run-all == 'true'
+    runs-on: ubuntu-latest
+    timeout-minutes: 90
+    steps:
+      - name: Clone
+        uses: actions/checkout@v6
+        with:
+          submodules: true
+      - name: Setup Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '1.25.4'
+      - name: Build parakeet-cpp backend image and run transcription gRPC e2e tests
+        run: |
+          make test-extra-backend-parakeet-cpp-transcription
   # VITS TTS via the sherpa-onnx backend. Drives both TTS (file write) and
   # TTSStream (PCM chunks) on the e2e-backends harness.
   tests-sherpa-onnx-grpc-tts: