Remove workflows irrelevant to this fork (auto-response, stale,
labeler, docker-release, install-smoke, formal-conformance,
sandbox-common-smoke). Slim ci.yml to just check + test jobs,
dropping iOS/macOS/Android/Windows/secrets/docs/release lanes.
Clean dependabot.yml of Swift and Gradle entries.
Co-authored-by: Cursor <cursoragent@cursor.com>