feat(prompt): add password input utility with masking

Adds new password prompt utility with customizable masking for secure
credential collection. Integrates with help command for improved UX.

src/commands/help-command.ts

@@ -151,16 +151,17 @@ Claude Code Profile & Model Switcher`.trim();
     'CLI Proxy (OAuth Providers)',
     [
       'Zero-config OAuth authentication via CLIProxyAPI',
-      'First run: Browser opens for authentication',
+      'First run: Browser opens for authentication, then model selection',
       'Settings: ~/.ccs/{provider}.settings.json (created after auth)',
     ],
     [
-      ['ccs gemini', 'Google Gemini (gemini-2.5-pro)'],
+      ['ccs gemini', 'Google Gemini (gemini-2.5-pro or 3-pro)'],
       ['ccs codex', 'OpenAI Codex (gpt-5.1-codex-max)'],
-      ['ccs agy', 'Antigravity (gemini-3-pro-preview)'],
+      ['ccs agy', 'Antigravity (Claude/Gemini models)'],
       ['ccs qwen', 'Qwen Code (qwen3-coder)'],
       ['', ''], // Spacer
       ['ccs <provider> --auth', 'Authenticate only'],
+      ['ccs <provider> --config', 'Change model (agy, gemini)'],
       ['ccs <provider> --logout', 'Clear authentication'],
       ['ccs <provider> --headless', 'Headless auth (for SSH)'],
       ['ccs codex "explain code"', 'Use with prompt'],