chore: simplify channel adapters

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

Author: bluedbird

config/system.yaml

@@ -10,13 +10,3 @@ telegram:
 provider:
   model: ""
   extraArgs: []
-
-# GitHub webhooks (requires GitHub App + tunnel)
-github:
-  enabled: false
-  token: ${GITHUB_TOKEN}
-  workflowsDir: ./workflows/github
-  webhook:
-    port: 3100
-    path: /webhooks/github
-    secret: ${GITHUB_WEBHOOK_SECRET}