feat(terminal): newline chord as registry data, plus a Key tester in Settings

capabilities.newline replaces choosing the Shift+Enter bytes in the send-key
route. Key tester shows the keydown/keypress/keyup a browser reports.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

config/test-suites.ts

@@ -31,6 +31,7 @@ export const BROWSER_TEST_GLOBS = [
   'test/capture-geometry-retry.browser.test.ts',
   'test/codex-predictive-echo.test.ts', // also needs a real codex binary
   'test/split-pane-terminal.browser.test.ts',
+  'test/key-tester.browser.test.ts',
   'test/split-pane-orchestration.browser.test.ts',
   'test/split-pane-auto-collapse.browser.test.ts',
 ];