fix(downloads): GIF review round 1 — shape, HDR, caps, audio, copy

- A GIF squares its pixels before the size, so an anamorphic source keeps
  its shown shape (a 720x480 DVD at 16:9 was 480x320).
- An editor GIF of an HDR upload is tonemapped, as a clip GIF is.
- The length caps are judged in whole milliseconds: a range exactly at a
  cap is no longer refused for a float hair over it.
- A GIF is made of a video only: an audio file is refused with its reason
  and the editor offers no GIF for it.
- A GIF clip keeps no audio track: the track neither splits its cache key
  nor fails it.
- The editor's GIF notes keep their live region mounted; one size reads
  as one ("about 1 MB"), none is shown with nothing kept; the size choices
  show their unit; a shared picture that fails to load says so.
- Copy: the two-sentence GIF notes keep their last stop (a copy-rule test
  now holds it); the English warns of "only a still picture".

backend/tests/test_edit_gif.py

@@ -3,12 +3,15 @@ to the GIF's limits at enqueue, and made by the worker with real ffmpeg."""
 
 import shutil
 import subprocess
+from pathlib import Path
 
 import pytest
 
 from app.config import settings
+from app.downloads import clip as clipmod
 from app.downloads import edit as editmod
 from app.downloads import pipeline, service
+from app.downloads import probe as probemod
 from app.downloads import gif as gifmod
 from app.downloads import upload as uploadmod
 from app.downloads.models import DownloadJob, MediaAsset
@@ -63,6 +66,84 @@ def test_a_gif_edit_it_cannot_make_is_refused_with_its_reason(
     assert e.value.reason == reason
 
 
+@needs_ffmpeg
+def test_a_gif_edit_of_exactly_thirty_seconds_is_allowed(db, make_user, tmp_path, monkeypatch):
+    monkeypatch.setattr(settings, "files_root", str(tmp_path / "root"))
+    u = make_user()
+    source = _source(db, u, tmp_path)
+    # Ends kept to the millisecond whose float difference lands a hair over 30 s.
+    assert 32.02 - 2.02 > gifmod.MAX_S
+    job = service.enqueue_edit(
+        db, u.id, source, {"trim": {"start_s": 2.02, "end_s": 32.02}, "gif": {"side": 480}}
+    )
+    assert job.edit_spec["gif"] == {"side": 480}
+
+
+@needs_ffmpeg
+def test_a_gif_is_made_of_a_video_never_of_audio(db, make_user, tmp_path, monkeypatch):
+    monkeypatch.setattr(settings, "files_root", str(tmp_path / "root"))
+    u = make_user()
+    src = tmp_path / "in.m4a"
+    subprocess.run(
+        [
+            "ffmpeg", "-y", "-loglevel", "error",
+            "-f", "lavfi", "-i", "sine=frequency=440:duration=10", "-c:a", "aac", str(src),
+        ],
+        check=True,
+    )  # fmt: skip
+    source = uploadmod.ingest_upload(
+        db, u.id, filename="in.m4a", src_path=src, size=src.stat().st_size
+    )
+    assert db.get(MediaAsset, source.asset_id).media_kind == "audio"
+    spec = {"trim": {"start_s": 1, "end_s": 5}}
+    with pytest.raises(service.EditError) as e:
+        service.enqueue_edit(db, u.id, source, {**spec, "gif": {"side": 480}})
+    assert e.value.reason == "gif_not_video"
+    # The same range as audio is an edit as it always was.
+    assert service.enqueue_edit(db, u.id, source, spec).edit_spec["trim"]["end_s"] == 5
+
+
+@needs_ffmpeg
+def test_an_hdr_source_is_tonemapped_before_its_gif_palette(db, make_user, tmp_path, monkeypatch):
+    monkeypatch.setattr(settings, "files_root", str(tmp_path / "root"))
+    u = make_user()
+    src = tmp_path / "hlg.mp4"
+    subprocess.run(
+        [
+            "ffmpeg", "-y", "-loglevel", "error",
+            "-f", "lavfi", "-i", "testsrc2=size=640x360:rate=10:duration=4",
+            "-vf", "setparams=color_trc=arib-std-b67:color_primaries=bt2020:colorspace=bt2020nc",
+            "-c:v", "libx264", "-pix_fmt", "yuv420p", str(src),
+        ],
+        check=True,
+    )  # fmt: skip
+    source = uploadmod.ingest_upload(
+        db, u.id, filename="hlg.mp4", src_path=src, size=src.stat().st_size
+    )
+    # The upload keeps its HLG tag, as an HDR phone video's does.
+    placed = Path(settings.files_root) / db.get(MediaAsset, source.asset_id).rel_path
+    assert clipmod.is_hdr(probemod.probe_json(placed) or {})
+    job = service.enqueue_edit(
+        db, u.id, source, {"trim": {"start_s": 1, "end_s": 3}, "gif": {"side": 320}}
+    )
+    asset = db.get(MediaAsset, job.asset_id)
+    job.status, asset.status = "running", "downloading"
+    db.commit()
+    seen: dict = {}
+    build = gifmod.build_cmd
+
+    def spy(*a, **k):
+        seen["pre"] = k["pre"]
+        return build(*a, **k)
+
+    monkeypatch.setattr(pipeline.gifmod, "build_cmd", spy)
+    pipeline._process_edit(job.id, asset.id)
+
+    assert "tonemap" in seen["pre"]
+    db.expire_all()
+    assert db.get(DownloadJob, job.id).status == "done"
+
+
 @needs_ffmpeg
 def test_a_gif_edit_is_made_by_the_worker_and_kept_as_an_image_file(
     db, make_user, tmp_path, monkeypatch