chore: drop source-attribution comments from provider code

Remove "Ported from OmniRoute" and cockpit-tools attribution comments.
User-Agent strings and README/landing credits are left intact.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

open-sse/handlers/search/callers.js

@@ -1,7 +1,6 @@
 /**
  * Search Provider Request Builders
  *
- * Ported from OmniRoute open-sse/handlers/search.ts (lines 223-610).
  * Builds HTTP request `{ url, init }` for 10 search providers.
  *
  * @typedef {Object} SearchProviderConfig