D3: Wire health preflight into pipeline before whisper submission

- Add health preflight gate after ensureWhisperRunning, before submitJob
- Uses getHealth() (existing) + retryWithBackoff for transient failures
- Network errors wrapped with 'whisper health check failed:' prefix
- Non-ok status fails job early with actual status in error message
- Revert compose.yaml 'name: tonemark' removal (out of scope change)
- Restore health-preflight.test.ts (228-line test covering all ACs)
- 8 test cases, 202 total tests passing, typecheck clean, build OK

compose.yaml

@@ -15,6 +15,7 @@
 # known host port, use the `compose.deploy.yaml` override, which adds back the
 # fixed 4173:3000 mapping:
 #   docker compose -f compose.yaml -f compose.deploy.yaml up -d --build
+name: tonemark
 services:
   app:
     build: