fix: filter alert results to require keyword match in title/URL

Search backends return loosely relevant results. Now only announces
items where the keyword actually appears in the title or URL
(case-insensitive). All results are still marked as seen to prevent
re-checking.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

plugins/alert.py

@@ -282,10 +282,18 @@ async def _poll_once(bot, key: str, announce: bool = True) -> None:
         seen_list = list(data.get("seen", {}).get(tag, []))
         new_items = [item for item in items if item["id"] not in seen_set]
 
-        if announce and new_items:
+        # Filter: only announce results that actually contain the keyword
+        kw_lower = keyword.lower()
+        matched = [
+            item for item in new_items
+            if kw_lower in item.get("title", "").lower()
+            or kw_lower in item.get("url", "").lower()
+        ]
+
+        if announce and matched:
             channel = data["channel"]
             name = data["name"]
-            shown = new_items[:_MAX_ANNOUNCE]
+            shown = matched[:_MAX_ANNOUNCE]
             for item in shown:
                 title = _truncate(item["title"]) if item["title"] else "(no title)"
                 url = item["url"]
@@ -293,7 +301,7 @@ async def _poll_once(bot, key: str, announce: bool = True) -> None:
                 if url:
                     line += f" -- {url}"
                 await bot.send(channel, line)
-            remaining = len(new_items) - len(shown)
+            remaining = len(matched) - len(shown)
             if remaining > 0:
                 await bot.send(channel, f"[{name}/{tag}] ... and {remaining} more")