feat: add video duration to YouTube announcements

Fetches duration via InnerTube player API for new videos at
announcement time. Displayed as compact h:mm:ss before views/likes.
Gracefully omitted for Shorts and unavailable content.

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

tests/test_youtube.py

@@ -24,6 +24,7 @@ from plugins.youtube import (  # noqa: E402
     _derive_name,
     _errors,
     _extract_channel_id,
+    _format_duration,
     _is_youtube_url,
     _load,
     _parse_feed,
@@ -827,18 +828,26 @@ class TestCmdYtCheck:
         }
         _save(bot, "#test:news", data)
 
+        def fake_duration(video_id):
+            return {"def456": 1105, "ghi789": 62}.get(video_id, 0)
+
         async def inner():
-            with patch.object(_mod, "_fetch_feed", _fake_fetch_ok):
+            with (
+                patch.object(_mod, "_fetch_feed", _fake_fetch_ok),
+                patch.object(_mod, "_fetch_duration", fake_duration),
+            ):
                 await cmd_yt(bot, _msg("!yt check news"))
             announcements = [s for t, s in bot.sent if t == "#test"]
             assert len(announcements) == 2
             assert "[news]" in announcements[0]
             assert "Calculus" in announcements[0]
-            # Verify metadata suffix (views, likes, date)
-            assert "| " in announcements[0]
+            # Verify metadata suffix (duration, views, likes, date)
+            assert "18:25" in announcements[0]
             assert "820kv" in announcements[0]
             assert "32klk" in announcements[0]
             assert "2026-02-01" in announcements[0]
+            # Second announcement has 1:02 duration
+            assert "1:02" in announcements[1]
 
         asyncio.run(inner())
 
@@ -930,7 +939,10 @@ class TestPollOnce:
         _channels[key] = data
 
         async def inner():
-            with patch.object(_mod, "_fetch_feed", fake_big):
+            with (
+                patch.object(_mod, "_fetch_feed", fake_big),
+                patch.object(_mod, "_fetch_duration", lambda vid: 0),
+            ):
                 await _poll_once(bot, key, announce=True)
             messages = [s for t, s in bot.sent if t == "#test"]
             # 5 individual + 1 "... and N more"
@@ -1177,3 +1189,33 @@ class TestCompactNum:
 
     def test_fractional_m(self):
         assert _compact_num(2_500_000) == "2.5M"
+
+
+# ---------------------------------------------------------------------------
+# TestFormatDuration
+# ---------------------------------------------------------------------------
+
+class TestFormatDuration:
+    def test_zero(self):
+        assert _format_duration(0) == ""
+
+    def test_negative(self):
+        assert _format_duration(-1) == ""
+
+    def test_seconds_only(self):
+        assert _format_duration(45) == "0:45"
+
+    def test_minutes_and_seconds(self):
+        assert _format_duration(125) == "2:05"
+
+    def test_exact_minutes(self):
+        assert _format_duration(600) == "10:00"
+
+    def test_hours(self):
+        assert _format_duration(3661) == "1:01:01"
+
+    def test_large_hours(self):
+        assert _format_duration(36000) == "10:00:00"
+
+    def test_one_second(self):
+        assert _format_duration(1) == "0:01"