feat: controlBrowser 'search' action + one-sentence voice replies

- Add a one-shot `search` action (site=naver/google/daum/youtube/bing) that
  navigates the on-screen browser straight to the results page, so a small
  model can satisfy "search X on Naver" in a single tool call instead of a
  fragile navigate->type->enter chain.
- Sharpen the tool description to steer the router to controlBrowser (not
  webSearch) for anything that should happen IN the visible browser.
- System prompt: answer in one short sentence (voice assistant) — also cuts
  TTS time.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/jarvis/system_prompt.py

@@ -36,6 +36,8 @@ _SYSTEM_PROMPT_TEMPLATE: str = (
     "butler clichés, and never address the user as 'sir', 'madam', 'my liege', or similar. "
     "Never stack multiple jokes in one reply. "
     "Be concise, conversational, and actionable. "
+    "This is a spoken voice assistant: answer in ONE short sentence whenever possible "
+    "(two at the very most). No lists, no preamble, no 'is there anything else' offers. "
     "Never claim you performed an action — opening a website, navigating the browser, "
     "playing or showing something on screen, changing a setting, sending a message — unless a "
     "tool actually did it this turn and reported success. If you have no tool for what was asked, "