test(tide-table): the OPAL title join needs the page to be as-performed

Audited what could have consumed the phantom SOUNDCHECK entry positionally.
Answer: nothing did. The two real consumers of setlist.entries() are safe --
take-segments.py builds a dict keyed by path stem (a phantom adds one unused
key) and migrate-columns.py calls tracks(), not entries(). No shipped artifact
was off by one.

But the audit found a different positional coupling, live and undocumented.
opal_title_map() joins tracks.json's 1..N performance order against
segments_v4.json's perf_track. OPAL was played as 15 tracks; the release cut
Desire, and segments_v4 renumbered around the hole -- its perf_track keys are
1..13 and 15, with no 14. So the join lines up only while Desire still holds
performance slot 14.

Measured both ways rather than argued: as-performed yields 14 mappings
including REVOLUTION; drop Desire to make the page match the release and it
falls to 13. REVOLUTION's title is LOST -- silently, with nothing mislabelled,
which is what would have made it hard to notice. PLN chose as-performed today
as a documentary call about the page; this join quietly depended on the same
answer, and nobody knew the two were connected.

So: the assumption is written down where the join lives, and three tests hold
it -- every released track gets a title, the encore by name, Desire maps to
nothing rather than borrowing a neighbour's, and the hole at perf_track 14 is
still really there. That last one matters: if segments_v4 is ever renumbered
densely the reasoning stops holding, and the right outcome is a red test
rather than a quietly missing track.

armada/tide-table/setlist_to_segments.py

@@ -48,6 +48,21 @@ def opal_title_map() -> dict[str, str]:
     The join key is performance order: `tracks.json` lists score paths 1..N in
     the order played, and `segments_v4.json` carries `perf_track` alongside the
     title that actually shipped on the file. Neither file alone has both halves.
+
+    THIS DEPENDS ON tracks.json BEING THE SET AS PERFORMED, and nothing in
+    either file used to say so. OPAL was played as 15 tracks; the release cut
+    Desire, and `segments_v4.json` renumbered around the hole -- its
+    `perf_track` keys are 1..13 and 15, with no 14. So the enumerate() below
+    only lines up while Desire still occupies performance slot 14 in
+    tracks.json.
+
+    Measured 2026-09-05, both ways: as-performed yields 14 mappings including
+    REVOLUTION. Drop Desire to make the page match the release and the count
+    falls to 13 -- REVOLUTION's title is LOST, silently, because i=14 then
+    points at a perf_track that does not exist. Nothing mislabels, which is
+    what would have made it hard to notice. PLN chose as-performed for the
+    page on 2026-09-05 (a documentary call, not a technical one); this join
+    quietly needs that same choice, and test_opal_title_map guards it.
     """
     tj = Path("/home/pln/Work/Web/www/content/lives/2026/opal-festival-2026/tracks.json")
     sv = Path("/home/pln/Work/Sound/Prod/Opal26_master/segments_v4.json")

armada/tide-table/tests/test_setlist_to_segments.py

+"""The OPAL title join, and the assumption it silently rests on.
+
+`opal_title_map()` joins tracks.json's 1..N performance order against
+segments_v4.json's `perf_track`. It is correct today, and it is correct only
+because the gig page documents the set AS PERFORMED: OPAL was played as 15
+tracks, the release cut Desire, and segments_v4's perf_track keys are 1..13
+and 15 with a hole at 14. Re-cut the page to the 14 released tracks and the
+enumerate() slides -- REVOLUTION's title vanishes with no error and no
+mislabel, which is the hard kind of wrong to see.
+
+So this asserts the OUTCOME (every released track gets its title) rather than
+the mechanism, and it asserts the hole is really there -- because if
+segments_v4 is ever renumbered densely, the reasoning above stops holding and
+somebody should be told by a red test rather than by a missing track.
+"""
+
+import json
+import sys
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
+
+import pytest  # noqa: E402
+
+import setlist_to_segments as sts  # noqa: E402
+
+TRACKS_JSON = Path("/home/pln/Work/Web/www/content/lives/2026/"
+                   "opal-festival-2026/tracks.json")
+SEGMENTS_V4 = Path("/home/pln/Work/Sound/Prod/Opal26_master/segments_v4.json")
+
+needs_files = pytest.mark.skipif(
+    not (TRACKS_JSON.exists() and SEGMENTS_V4.exists()),
+    reason="OPAL release artifacts not on this box")
+
+
+@needs_files
+def test_every_released_track_gets_its_title():
+    m = sts.opal_title_map()
+    segments = json.loads(SEGMENTS_V4.read_text())
+    assert len(m) == len(segments), (
+        f"{len(segments)} tracks shipped but only {len(m)} got a title -- the "
+        f"positional join has slipped. Missing titles: "
+        f"{sorted(set(r['title'] for r in segments) - set(m.values()))}")
+    # The encore is the one the slip would drop first, so name it explicitly.
+    assert "the_revolution_will_be_sampled" in m, \
+        "REVOLUTION lost its title: tracks.json is probably no longer the " \
+        "set as performed (Desire must keep performance slot 14)"
+    assert m["the_revolution_will_be_sampled"] == "REVOLUTION"
+
+
+@needs_files
+def test_the_assumption_is_still_true():
+    """tracks.json is as-performed, and segments_v4 has the hole."""
+    scores = [t.get("file") or "" for t in
+              json.loads(TRACKS_JSON.read_text())["tracks"]]
+    perf = sorted(r["perf_track"] for r in
+                  json.loads(SEGMENTS_V4.read_text()))
+
+    assert any("desire" in s.lower() for s in scores), (
+        "Desire is gone from tracks.json, so the page is the RELEASE, not the "
+        "performance -- opal_title_map()'s enumerate() no longer lines up with "
+        "perf_track and REVOLUTION will silently lose its title")
+    assert len(scores) == len(perf) + 1, (
+        f"{len(scores)} performed vs {len(perf)} released: expected exactly "
+        f"one performed-but-unreleased track (Desire)")
+    assert 14 not in perf and 15 in perf, (
+        f"segments_v4 perf_track = {perf}. The hole at 14 is what makes the "
+        f"positional join work; if these were renumbered densely, "
+        f"opal_title_map() needs rewriting, not this test relaxing")
+
+
+@needs_files
+def test_desire_is_deliberately_unmapped():
+    """It has no v4 segment, so it must map to nothing -- not to a neighbour."""
+    m = sts.opal_title_map()
+    assert "desire" not in m, \
+        "Desire was cut from the release; a title here means the join " \
+        "borrowed one from an adjacent track"