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

internal/llm/remote.go

@@ -132,6 +132,9 @@ func (p *Pair) probe(ctx context.Context) {
 		p.set(false)
 		return
 	}
+	if p.remote != nil {
+		p.remote.authorize(req)
+	}
 	resp, err := p.http.Do(req)
 	if err != nil {
 		p.set(false)