chore: cleanup unused files and consolidate tests

- Remove unused .config/isolated-tests.json (empty config)
- Remove duplicate test/argv/flags.test.ts (kept more comprehensive test/argv-flags.test.ts with 106 tests vs 76)
- Update plugins/README.md description for clarity
- Remove .DS_Store file

All tests pass (4489 tests, 84.19% cumulative coverage)

Author: jdalton

.config/isolated-tests.json

@@ -1,6 +1,6 @@
 # Babel Plugins
 
-Shared transformation plugins for Socket registry builds.
+Babel transformation plugins exported by `@socketsecurity/lib`.
 
 ## `babel-plugin-inline-require-calls`