feat(brain): wire STREAM_BROWSER real-time modes into the reply engine (browser + Gemini)

Completes the two info modes in the Python brain:

- config.py: read STREAM_BROWSER / GEMINI_API_KEY / GEMINI_MODEL from env into
  Settings (stream_browser, gemini_api_key, gemini_model). Verified load_settings
  reads both modes.
- realtime_search.py: two fail-open backends returning the same fenced
  UNTRUSTED-WEB-EXTRACT envelope: browser_search() shells the Node CDP helper to
  drive the on-screen Chrome (visible on the broadcast); gemini_search() calls
  the Gemini REST API with google_search grounding.
- web_search.run(): routes by mode before the DDG cascade (true->browser,
  false->Gemini), falling through to DDG/Brave/Wikipedia on any miss.
- browse_and_play tool: plays a YouTube video on the shared screen (true mode
  only); registered in the tool registry.
- specs + docs/llm_contexts.md updated (new Gemini LLM context); CLAUDE.md spec
  registry updated.

Verified live against the running Chrome: true-mode webSearch returned real
Google results for "오늘 서울 날씨", browseAndPlay played the IU 밤편지 MV, and
false-mode degrades gracefully on a bad/absent key. A valid GEMINI_API_KEY is
still needed to confirm the real Gemini grounding output.

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

src/jarvis/tools/builtin/browse_and_play.py

@@ -0,0 +1,83 @@
+"""Play a YouTube video on the shared screen (browser/screen-share mode).
+
+Only meaningful when ``STREAM_BROWSER`` is true: it drives the on-screen Chrome
+(via the Node CDP helper) to search YouTube and play the first result, which is
+visible on the Go-Live broadcast. In voice-only mode (false) there is nothing to
+show, so the tool reports that and does nothing.
+"""
+
+from __future__ import annotations
+
+import json
+import os
+import subprocess
+from typing import Dict, Any, Optional
+
+from ..base import Tool, ToolContext
+from ..types import ToolExecutionResult
+from ...debug import debug_log
+from .realtime_search import _NODE_SCRIPT
+
+
+class BrowseAndPlayTool(Tool):
+    """Play a YouTube video on the shared screen."""
+
+    @property
+    def name(self) -> str:
+        return "browseAndPlay"
+
+    @property
+    def description(self) -> str:
+        return (
+            "Play a song / music video / clip on the shared screen by searching YouTube "
+            "and playing the first result. Use when the user asks you to play or watch "
+            "something. Only available in screen-share mode."
+        )
+
+    @property
+    def inputSchema(self) -> Dict[str, Any]:
+        return {
+            "type": "object",
+            "properties": {
+                "query": {
+                    "type": "string",
+                    "description": "What to play, e.g. 'IU Good Day' or 'lofi hip hop'.",
+                }
+            },
+            "required": ["query"],
+        }
+
+    def run(self, args: Optional[Dict[str, Any]], context: ToolContext) -> ToolExecutionResult:
+        cfg = context.cfg
+        if not getattr(cfg, "stream_browser", True):
+            return ToolExecutionResult(
+                success=False,
+                reply_text="화면 공유 모드(STREAM_BROWSER=true)에서만 영상을 재생할 수 있습니다.",
+            )
+        query = ""
+        if args and isinstance(args, dict):
+            query = str(args.get("query", "")).strip()
+        if not query:
+            return ToolExecutionResult(success=False, reply_text="재생할 내용을 알려주세요.")
+        if not _NODE_SCRIPT.exists():
+            return ToolExecutionResult(success=False, reply_text="브라우저 재생 도구를 찾을 수 없습니다.")
+
+        context.user_print(f"▶️ 화면에서 '{query}' 재생 중…")
+        debug_log(f"    ▶️ browseAndPlay '{query}'", "tools")
+        try:
+            proc = subprocess.run(
+                ["node", str(_NODE_SCRIPT), query, "youtube"],
+                capture_output=True,
+                text=True,
+                timeout=40,
+                env={**os.environ, "CDP_PORT": os.environ.get("CDP_PORT", "9222")},
+            )
+            data = json.loads((proc.stdout or "").strip() or "{}")
+        except Exception as e:
+            return ToolExecutionResult(success=False, reply_text=f"재생에 실패했습니다: {e}")
+        if not data.get("ok"):
+            return ToolExecutionResult(
+                success=False, reply_text=f"재생에 실패했습니다: {data.get('error', 'unknown')}"
+            )
+        title = data.get("title") or query
+        return ToolExecutionResult(success=True, reply_text=f"화면에서 '{title}' 재생을 시작했습니다.")