Episode names: render MAL titles on the episode grid

anidb's episodes API has no names (id/number/filler only), but the
Jikan call we already make for intro timings carries them (title +
title_japanese). _parse_intros now keeps one entry per episode with
title and optional start/length (entries are never null anymore).

Client: attachEpNames() reuses the introCache promise, stamps
epsList[i].name, re-renders; buttons show the name (3-line clamp) +
full tooltip. Jikan down => no names, no error (same graceful
degradation as the skip-intro button).

Verified headless: Jujutsu Kaisen S1 24/24 buttons named
('E1 | Ryomen Sukuna' ...); S2 (Jikan 504 at the time) rendered
gracefully without names. 17/17 API tests.

tests/test_api.py

@@ -301,17 +301,19 @@ def _search_count(user):
 def test_parse_intros():
     from server.upstream import _parse_intros
     out = _parse_intros([
-        {"intro": {"start": 95, "length": 60}},
+        {"intro": {"start": 95, "length": 60}, "title": "Ryomen Sukuna"},
         {"intro": {"start": 0, "length": 0}},   # MAL "no intro" marker
-        {"intro": None},
+        {"intro": None, "title": "Named, no timing"},
         {},
     ])
     assert out == [
-        {"start": 95, "length": 60},
-        {"start": 0, "length": 0},
-        None,
-        None,
+        {"title": "Ryomen Sukuna", "start": 95, "length": 60},
+        {"title": None, "start": 0, "length": 0},
+        {"title": "Named, no timing"},
+        {"title": None},
     ]
+    # setupIntro relies on `t.length` being absent (falsy) when no timing
+    assert "start" not in out[2]
 
 
 def test_intros_parses_jikan_shapes():
@@ -330,8 +332,8 @@ def test_intros_parses_jikan_shapes():
     u._CACHE.clear()
     u._get = lambda url: R()  # stub the network
     assert u._intros(92573) == [
-        {"start": 111, "length": 77},
-        {"start": 0, "length": 0},
+        {"title": "Episode 1", "start": 111, "length": 77},
+        {"title": "Episode 2", "start": 0, "length": 0},
     ]
     # wrapped shape still works
     class W: