#18823: revert(browser): remove extraArgs config

## Summary - Revert browser.extraArgs support and related tests/config additions. - Removes extra Chrome arg injection to undo accidental merge. ## Testing - Not run (revert only). Reverts: https://github.com/openclaw/openclaw/pull/18443 <!-- greptile_comment --> <h3>Greptile Summary</h3> This PR cleanly reverts the `browser.extraArgs` configuration feature that was added in three commits (039fc1e0, 2977f732, 47f8c920). The revert removes: - The `extraArgs` property from `BrowserConfig` type definition - The `extraArgs` field from `ResolvedBrowserConfig` - The filtering/validation logic for `extraArgs` in `resolveBrowserConfig()` - The Chrome argument injection code in `launchOpenClawChrome()` - The `extraArgs: []` initialization in `buildSandboxBrowserResolvedConfig()` - All 5 test cases covering `extraArgs` behavior The revert is complete and doesn't leave any dangling references. All changes are pure deletions that undo the original feature without introducing new logic. <h3>Confidence Score: 5/5</h3> - This PR is safe to merge with minimal risk - The revert is complete and correct. All additions from the three commits being reverted (039fc1e0, 2977f732, 47f8c920) have been cleanly removed. No dangling references to `extraArgs` remain in the TypeScript/JavaScript codebase. The changes are pure deletions with no new logic introduced, making this a straightforward and safe revert operation. - No files require special attention _{Last reviewed commit: d03339a} <!-- greptile_other_comments_section --> <!-- /greptile_comment -->