feat(linq): add interactive onboarding adapter

Walk users through Linq setup via `openclaw channels add` wizard
instead of requiring manual JSON config editing. Prompts for API
token, phone number, and webhook config with sensible defaults.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/plugin-sdk/index.ts

@@ -458,6 +458,7 @@ export {
   resolveLinqAccount,
   type ResolvedLinqAccount,
 } from "../linq/accounts.js";
+export { linqOnboardingAdapter } from "../channels/plugins/onboarding/linq.js";
 export type { LinqProbe } from "../linq/types.js";
 
 // Media utilities