feat: metadata enrichment for alerts and subscription plugins

Alert backends now populate structured `extra` field with engagement
metrics (views, stars, votes, etc.) instead of embedding them in titles.
Subscription plugins show richer announcements: Twitch viewer counts,
YouTube views/likes/dates, RSS published dates.

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

plugins/rss.py

@@ -135,6 +135,21 @@ def _fetch_feed(url: str, etag: str = "", last_modified: str = "") -> dict:
 
 # -- Feed parsing ------------------------------------------------------------
 
+def _parse_date(raw: str) -> str:
+    """Try to extract a YYYY-MM-DD date from a raw date string."""
+    import re as _re
+    m = _re.search(r"\d{4}-\d{2}-\d{2}", raw)
+    if m:
+        return m.group(0)
+    # Try RFC 2822 (common in RSS pubDate)
+    from email.utils import parsedate_to_datetime
+    try:
+        dt = parsedate_to_datetime(raw)
+        return dt.strftime("%Y-%m-%d")
+    except (ValueError, TypeError):
+        return ""
+
+
 def _parse_rss(root: ET.Element) -> tuple[str, list[dict]]:
     """Parse RSS 2.0 feed."""
     channel = root.find("channel")
@@ -146,8 +161,13 @@ def _parse_rss(root: ET.Element) -> tuple[str, list[dict]]:
         item_id = item.findtext("guid") or item.findtext("link") or ""
         item_title = (item.findtext("title") or "").strip()
         item_link = (item.findtext("link") or "").strip()
+        pub_date = (item.findtext("pubDate") or "").strip()
+        date = _parse_date(pub_date) if pub_date else ""
         if item_id:
-            items.append({"id": item_id, "title": item_title, "link": item_link})
+            items.append({
+                "id": item_id, "title": item_title,
+                "link": item_link, "date": date,
+            })
     return (title, items)
 
 
@@ -162,8 +182,14 @@ def _parse_atom(root: ET.Element) -> tuple[str, list[dict]]:
         if not entry_id:
             entry_id = entry_link
         entry_title = (entry.findtext(f"{_ATOM_NS}title") or "").strip()
+        published = (entry.findtext(f"{_ATOM_NS}published") or "").strip()
+        updated = (entry.findtext(f"{_ATOM_NS}updated") or "").strip()
+        date = _parse_date(published or updated)
         if entry_id:
-            items.append({"id": entry_id, "title": entry_title, "link": entry_link})
+            items.append({
+                "id": entry_id, "title": entry_title,
+                "link": entry_link, "date": date,
+            })
     return (title, items)
 
 
@@ -246,7 +272,10 @@ async def _poll_once(bot, key: str, announce: bool = True) -> None:
         for item in shown:
             title = _truncate(item["title"]) if item["title"] else "(no title)"
             link = item["link"]
+            date = item.get("date", "")
             line = f"[{name}] {title}"
+            if date:
+                line += f" | {date}"
             if link:
                 line += f" -- {link}"
             await bot.send(channel, line)