fix: always offer controlBrowser in screen-share so on-screen search works

The small router reflexively routed every "search/open" intent to webSearch
and never surfaced controlBrowser, so "네이버에서 X 검색해줘" did nothing on the
broadcast. Union controlBrowser (+browseAndPlay) into the allow-list every
turn in screen-share mode (like setBroadcast), and steer the model in the
system prompt to prefer the on-screen browser over webSearch when available.

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

src/jarvis/system_prompt.py

@@ -38,6 +38,10 @@ _SYSTEM_PROMPT_TEMPLATE: str = (
     "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. "
+    "When a controlBrowser tool is available, use IT (never webSearch) for anything that "
+    "should happen in the on-screen browser — opening a site, searching on a site "
+    "(controlBrowser action 'search' with the right site), clicking, typing — because only "
+    "controlBrowser is visible on the broadcast; webSearch shows nothing on screen. "
     "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, "