feat: play the Nth YouTube result in browseAndPlay via an index arg

agents/llm.md promises "play the Nth video from the top", but browseAndPlay
only ever clicked the first result. Add an optional 1-based index argument
(default 1, backward-compatible) threaded to the Node helper, which now clicks
the Nth a#video-title and clamps to the number of results returned so asking
beyond the list plays the last available video instead of failing.

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

src/jarvis/tools/builtin/browse_and_play.py

@@ -30,8 +30,10 @@ class BrowseAndPlayTool(Tool):
     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."
+            "and playing a result. Use when the user asks you to play or watch "
+            "something. Plays the first result by default; pass 'index' to play the "
+            "Nth result from the top of the search list (e.g. 'play the 3rd video' -> "
+            "index=3). Only available in screen-share mode."
         )
 
     @property
@@ -42,7 +44,16 @@ class BrowseAndPlayTool(Tool):
                 "query": {
                     "type": "string",
                     "description": "What to play, e.g. 'IU Good Day' or 'lofi hip hop'.",
-                }
+                },
+                "index": {
+                    "type": "integer",
+                    "description": (
+                        "1-based position of the video to play in the search results, "
+                        "counted from the top of the list. Defaults to 1 (first result). "
+                        "Use for 'play the Nth video' / 'play the second one'."
+                    ),
+                    "minimum": 1,
+                },
             },
             "required": ["query"],
         }
@@ -55,18 +66,25 @@ class BrowseAndPlayTool(Tool):
                 reply_text="화면 공유 모드(STREAM_BROWSER=true)에서만 영상을 재생할 수 있습니다.",
             )
         query = ""
+        index = 1
         if args and isinstance(args, dict):
             query = str(args.get("query", "")).strip()
+            try:
+                index = int(args.get("index", 1) or 1)
+            except (TypeError, ValueError):
+                index = 1
+            if index < 1:
+                index = 1
         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")
+        context.user_print(f"▶️ 화면에서 '{query}' 재생 중… (#{index})")
+        debug_log(f"    ▶️ browseAndPlay '{query}' index={index}", "tools")
         try:
             proc = subprocess.run(
-                ["node", str(_NODE_SCRIPT), query, "youtube"],
+                ["node", str(_NODE_SCRIPT), query, "youtube", str(index)],
                 capture_output=True,
                 text=True,
                 timeout=40,