Grok preflight rejects deployment-key logins and accepts an unlisted default model #131

preflightPassed for Grok (run.ts, after #130) has two gaps. Both reproduce on main c3a177d with a stand-in grok whose grok models prints the text below and whose model call succeeds.

1. Deployment-key logins fail. grok 1.0.46 prints You are authenticated via deployment key. for that login. The pass check accepts only logged in or You are using XAI_API_KEY., so the runner retries once and records unauthenticated (exit 77) without running the model.

   You are authenticated via deployment key.
   Available models:
     * grok-4.7 (default)
   

2. An unlisted default model passes. grok prints Default model: <slug> (not in the list below) when the configured default is missing from the account's list. grokModelAvailable matches that line as a whole token, so a lane for grok-4.7 passes preflight even though only grok-4.6 is listed.

   You are logged in with grok.com.
   Default model: grok-4.7 (not in the list below)
   Available models:
     * grok-4.6
   

Expected: case 1 passes preflight; case 2 fails with unavailable-model (exit 69) before the model call. A fix could accept the deployment-key line and match the model only against the lines under Available models:.