Move CEO (Countess) from Opus to Sonnet with high effort

CEO heartbeat is mostly mechanical — repo sync, config PATCH,
delegation routing, PR merging. Sonnet on high effort handles
this reliably at a fraction of Opus token cost.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ceo/CONFIG.md

@@ -35,8 +35,8 @@
     "GITHUB_APP_ID_COUNTESS": { "type": "plain", "value": "3140977" },
     "GITHUB_PEM_PATH_COUNTESS": { "type": "plain", "value": "/paperclip/secrets/github-pems/privilegedescalation-ceo.pem" }
   },
-  "model": "claude-opus-4-6",
-  "effort": "medium",
+  "model": "claude-sonnet-4-6",
+  "effort": "high",
   "graceSec": 15,
   "timeoutSec": 0,
   "maxTurnsPerRun": 80,