feat(onboard): support non-interactive GitHub Copilot token auth

Add manifest-owned GitHub Copilot token support for non-interactive onboarding, including documented env fallback, ref-mode tokenRef storage, saved-profile reuse, and default model wiring that preserves existing primary model configuration.

Validation:
- pnpm test extensions/github-copilot/index.test.ts src/plugins/contracts/registry.contract.test.ts src/commands/onboard-non-interactive/local/auth-choice-inference.test.ts
- pnpm check:changed
- CI green on aadac2c8d4

extensions/github-copilot/openclaw.plugin.json

@@ -17,7 +17,11 @@
       "choiceHint": "Device login with your GitHub account",
       "groupId": "copilot",
       "groupLabel": "Copilot",
-      "groupHint": "GitHub + local proxy"
+      "groupHint": "GitHub + local proxy",
+      "optionKey": "githubCopilotToken",
+      "cliFlag": "--github-copilot-token",
+      "cliOption": "--github-copilot-token <token>",
+      "cliDescription": "GitHub Copilot OAuth token"
     }
   ],
   "configSchema": {