fix(hub): a show opens on its first season, not its first thumbnail

Reported live: a show with a dozen seasons opened on season 6. Every season
was in the picker and none was missing — the default was wrong.

VideoDetailModal took it from `repEntry.season`. `repEntry` is the show's
"representative entry", which the poster grid picks as
`episodes.find((e) => e.thumb_hash) || episodes[0]`: the first episode that
has a thumbnail, so the card has a fallback frame when TMDB has no poster.
That is from the original Videos commit; the season tabs came later and read
the same entry as "the episode the reader is looking at", which it never was
on that path. Episodes are sorted by (season, episode), so a show whose first
five seasons had no thumbnail yet — a partial enrichment pass, or ffmpeg
failing on those files — hands back a season-6 episode.

`defaultSeason(show)` reads the season list and nothing else: the lowest
season present, specials only when there is nothing else, and the lowest
*number* rather than the first entry so it does not quietly depend on
buildSeasons keeping its sort. The effect's dependency on repEntry goes with
it — nothing in it reads that any more.

test_video_default_season.py runs the function in node. No input it takes can
carry a thumbnail, which is the point. docs/mediacenter.md §10.5.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014UtzVrzM7e2tG9fSpkR9ML

1 files changed, 107 insertions, 0 deletions

diff --git a/packages/meshbay-hub/tests/test_video_default_season.py b/packages/meshbay-hub/tests/test_video_default_season.py
new file mode 100644
index 0000000..898d3f5
--- /dev/null
+++ b/packages/meshbay-hub/tests/test_video_default_season.py
@@ -0,0 +1,107 @@
+"""
+Which season a show's detail modal opens on.
+
+Reported live: a show with a dozen seasons opened on season 6. Every season was
+in the list and none was missing — the *default* was wrong, which is the harder
+kind to notice and the easier kind to shrug at.
+
+`VideoDetailModal` took it from `repEntry.season`. `repEntry` is the show's
+"representative entry", and the poster grid picks it as
+`episodes.find((e) => e.thumb_hash) || episodes[0]` — the first episode that
+has a thumbnail, so the card has a fallback frame when TMDB has no poster
+(`6af05ab`). The season tabs then read that same entry as "the episode the
+reader is looking at" (`0b0da86`), which it never was on that path. With the
+episodes sorted by (season, episode), a show whose first five seasons had no
+thumbnail yet — a partial enrichment pass, or ffmpeg failing on those
+particular files — hands back a season-6 episode, and the modal opens there.
+
+Two different meanings of "representative" that were never the same thing. The
+default is now `defaultSeason(show)`, which reads the season list and nothing
+else, and this holds it to that: no input here carries a thumbnail at all.
+
+The function is read out of `video-app.js` rather than duplicated — a copy
+would keep passing after the original changed.
+"""
+
+import json
+import re
+import shutil
+import subprocess
+from pathlib import Path
+
+import pytest
+
+STATIC = Path(__file__).resolve().parents[1] / "src" / "meshbay_hub" / "static"
+APP = STATIC / "video-app.js"
+
+pytestmark = pytest.mark.skipif(
+    shutil.which("node") is None or not APP.exists(),
+    reason="node or the SPA sources are not available")
+
+BLOCK = re.compile(r"^function defaultSeason\(show\) \{.*?^\}", re.M | re.S)
+
+
+@pytest.fixture(scope="module")
+def source():
+    m = BLOCK.search(APP.read_text())
+    assert m, ("defaultSeason is no longer where this test reads it from — the "
+               "season a show opens on is untested until this is fixed")
+    return m.group(0)
+
+
+def _default(tmp_path, source, seasons):
+    """`seasons` as `buildSeasons` returns them: ascending, specials first."""
+    show = None if seasons is None else {
+        "seasons": [{"season": n, "episodes": []} for n in seasons]}
+    script = tmp_path / "case.js"
+    script.write_text(f"""
+        {source}
+        console.log(JSON.stringify(defaultSeason({json.dumps(show)})));
+    """)
+    proc = subprocess.run(["node", str(script)], capture_output=True, text=True)
+    assert proc.returncode == 0, proc.stderr
+    return json.loads(proc.stdout)
+
+
+def test_a_show_opens_on_its_first_season(tmp_path, source):
+    assert _default(tmp_path, source, [1, 2, 3, 4, 5, 6, 7, 8]) == 1
+
+
+def test_specials_do_not_become_the_default(tmp_path, source):
+    """`buildSeasons` sorts ascending, so season 0 is first in the list and
+    would win a naive `seasons[0]`. Nobody means the extras by "the start"."""
+    assert _default(tmp_path, source, [0, 1, 2, 3]) == 1
+
+
+def test_a_show_of_nothing_but_specials_opens_on_them(tmp_path, source):
+    """The one case where season 0 is the right answer: there is no other."""
+    assert _default(tmp_path, source, [0]) == 0
+
+
+def test_a_show_that_starts_at_season_two_opens_there(tmp_path, source):
+    """Half a show on disk is ordinary. The first season *present* is the
+    answer, not the number 1, which would select a season that is not there
+    and filter the episode list down to nothing."""
+    assert _default(tmp_path, source, [2, 3, 4]) == 2
+
+
+def test_the_answer_does_not_depend_on_which_episode_has_a_thumbnail(tmp_path, source):
+    """The defect, as the shape of the input.
+
+    `defaultSeason` is handed the season list and nothing else — there is no
+    episode, no `thumb_hash`, no representative entry to be misled by. That is
+    the fix: the reported show opened on season 6 because its first five
+    seasons had no thumbnails yet, and no argument here can carry that.
+    """
+    reported = list(range(1, 9))
+    assert _default(tmp_path, source, reported) == 1
+    assert _default(tmp_path, source, list(reversed(reported))) == 1, (
+        "the first *season*, not the first entry in whatever order the list "
+        "arrived in")
+
+
+@pytest.mark.parametrize("show", [None, []])
+def test_no_seasons_means_no_selection(tmp_path, source, show):
+    """A movie has no `show` at all, and an empty one must not throw: the
+    modal renders no picker and `selectedSeason` stays null."""
+    assert _default(tmp_path, source, show) is None