Sign the completion and the probe with the same token (V-673)

llm.Client carries a bearer credential and sets it on the completion, and
Pair signs the /health probe with it too. An unsigned probe would answer 401,
Pair would read that as a card that is busy, and every workstation turn would
fall back to the resident model with nothing naming why.

The token comes from workstation.token, expanded from MAVEN_GPU_TOKEN like
every other secret in that file. Missing, and voicewire says so at startup:
the fallback is silent by design and this failure would otherwise be
invisible.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ESv8hqNPseYt1CnotZpqDz

cmd/mavend/voicewire.go

@@ -386,8 +386,13 @@ func modelSeam(cfg *config.Config, resident *llm.Client) (router.Completer, *llm
 		return resident, nil
 	}
 	ws := cfg.Workstation
+	remote := llm.New(ws.URL, time.Duration(ws.Timeout))
+	remote.SetToken(ws.Token)
+	if ws.Token == "" {
+		log.Printf("voice: no workstation.token — mavgpud refuses an unauthenticated request, so this reads as a card that is always busy")
+	}
 	pair := llm.NewPair(
-		llm.New(ws.URL, time.Duration(ws.Timeout)),
+		remote,
 		resident,
 		ws.Health,
 		time.Duration(ws.Probe),