feat(cli): add top-level /reload command to refresh all systems

- Consolidates existing reload subcommands (/agents, /commands, /extensions, /mcp, /memory, /skills) into a single top-level /reload (alias /refresh) command.
- Adds support for refreshing settings.json from disk via LoadedSettings.reload().
- Updates all relevant tests for LoadedSettings constructor changes.

packages/cli/src/ui/utils/MarkdownDisplay.test.tsx

@@ -213,6 +213,7 @@ Another paragraph.
         { path: '', settings: {}, originalSettings: {} },
         true,
         [],
+        '',
       );
 
       const { lastFrame, unmount } = await renderWithProviders(