fix(example-images): read real dimensions for imported videos, fixes #1115

Example videos added through the "Add examples" flow were stored with a
hardcoded 720x1280 entry. The dimension probe next to it only ran for
images (PIL cannot open .mp4/.webm files), so every video entry stayed
portrait regardless of the source. The showcase viewer then sizes its
container straight from that value (--media-aspect in showcase.css), so
landscape clips were letterboxed inside a 9:16 box. CivitAI-sourced
examples were unaffected because their dimensions come from the API.

PIL cannot read video containers, so add a dependency-free reader that
parses the container headers instead: moov/trak/tkhd for ISO base media
(with the sample description as a fallback), Segment/Tracks/Pixel* for
WebM/Matroska, and RIFF/WebP for animated examples saved with a video
extension. The sniffed signature decides which reader runs, so a .mp4
that is really WebM still reports the right size; the extension is only
a fallback. Both readers seek past mdat rather than reading it, so a
large file costs the same as a small one.

Imported entries now record the file's real size and keep the previous
placeholder only when the file cannot be parsed.

Existing libraries keep their wrong entries, so backfill them once via
the existing naming migration: bump CURRENT_NAMING_VERSION to 3 and
repair each model's empty-url entries from the files on disk, then sync
the scanner cache. Only entries with no remote url are touched -- those
have no other source, which makes the rewrite lossless -- and entries
already carrying the right size are left byte-identical, so the pass is
idempotent and a no-op for libraries that never imported a video.

tests/utils/test_example_images_metadata.py

@@ -9,6 +9,7 @@ from typing import Any, Dict, List, Tuple
 import pytest
 
 from py.utils import example_images_metadata as metadata_module
+from tests.utils.test_video_dimension_probe import build_mp4, build_webm
 
 
 class StubScanner:
@@ -216,4 +217,128 @@ async def test_update_metadata_from_local_examples_generates_entries(monkeypatch
         str(model_dir),
     )
     assert success is True
-    assert model_data["civitai"]["images"]
+    assert model_data["civitai"]["images"]
+
+
+async def test_update_metadata_after_import_uses_real_video_dimensions(
+    monkeypatch: pytest.MonkeyPatch, tmp_path, patch_metadata_manager
+):
+    """Regression: imported videos must not fall back to the 720x1280 default.
+
+    See issue #1115 — landscape videos were stored as portrait, so the showcase
+    viewer letterboxed them into a 9:16 container.
+    """
+
+    model_hash = "d" * 64
+    model_file = tmp_path / "video-model.safetensors"
+    model_file.write_text("content", encoding="utf-8")
+    model_data = {
+        "model_name": "VideoExample",
+        "file_path": str(model_file),
+        "civitai": {},
+    }
+    scanner = StubScanner([model_data])
+
+    video_path = tmp_path / "custom_abc.mp4"
+    video_path.write_bytes(build_mp4(1280, 720))
+
+    monkeypatch.setattr(metadata_module.ExifUtils, "extract_image_metadata", staticmethod(lambda _path: None))
+
+    _regular, custom = await metadata_module.MetadataUpdater.update_metadata_after_import(
+        model_hash,
+        model_data,
+        scanner,
+        [(str(video_path), "abc")],
+    )
+
+    assert custom[0]["type"] == "video"
+    assert (custom[0]["width"], custom[0]["height"]) == (1280, 720)
+    assert patch_metadata_manager[-1][1]["civitai"]["customImages"][0]["width"] == 1280
+
+
+async def test_update_metadata_after_import_uses_real_webm_dimensions(
+    monkeypatch: pytest.MonkeyPatch, tmp_path, patch_metadata_manager
+):
+    model_hash = "e" * 64
+    model_file = tmp_path / "webm-model.safetensors"
+    model_file.write_text("content", encoding="utf-8")
+    model_data = {
+        "model_name": "WebmExample",
+        "file_path": str(model_file),
+        "civitai": {},
+    }
+
+    video_path = tmp_path / "custom_def.webm"
+    video_path.write_bytes(build_webm(480, 832))
+
+    monkeypatch.setattr(metadata_module.ExifUtils, "extract_image_metadata", staticmethod(lambda _path: None))
+
+    _regular, custom = await metadata_module.MetadataUpdater.update_metadata_after_import(
+        model_hash,
+        model_data,
+        StubScanner([model_data]),
+        [(str(video_path), "def")],
+    )
+
+    assert (custom[0]["width"], custom[0]["height"]) == (480, 832)
+
+
+async def test_update_metadata_after_import_falls_back_for_unreadable_video(
+    monkeypatch: pytest.MonkeyPatch, tmp_path, patch_metadata_manager
+):
+    """An unparsable video keeps the legacy placeholder rather than failing."""
+
+    model_hash = "f" * 64
+    model_file = tmp_path / "broken-model.safetensors"
+    model_file.write_text("content", encoding="utf-8")
+    model_data = {
+        "model_name": "BrokenExample",
+        "file_path": str(model_file),
+        "civitai": {},
+    }
+
+    video_path = tmp_path / "custom_ghi.mp4"
+    video_path.write_bytes(b"\x00\x00\x00\x20ftypisom" + b"\xff" * 32)
+
+    monkeypatch.setattr(metadata_module.ExifUtils, "extract_image_metadata", staticmethod(lambda _path: None))
+
+    _regular, custom = await metadata_module.MetadataUpdater.update_metadata_after_import(
+        model_hash,
+        model_data,
+        StubScanner([model_data]),
+        [(str(video_path), "ghi")],
+    )
+
+    assert (custom[0]["width"], custom[0]["height"]) == (720, 1280)
+
+
+async def test_update_metadata_from_local_examples_uses_real_video_dimensions(
+    monkeypatch: pytest.MonkeyPatch, tmp_path
+):
+    model_hash = "1" * 64
+    model_dir = tmp_path / model_hash
+    model_dir.mkdir()
+    (model_dir / "clip.mp4").write_bytes(build_mp4(1920, 1080))
+    model_data: Dict[str, Any] = {
+        "model_name": "LocalVideo",
+        "civitai": {},
+        "file_path": str(tmp_path / "model.safetensors"),
+    }
+
+    async def fake_save(path, metadata):
+        return True
+
+    monkeypatch.setattr(metadata_module.MetadataManager, "save_metadata", staticmethod(fake_save))
+
+    success = await metadata_module.MetadataUpdater.update_metadata_from_local_examples(
+        model_hash,
+        model_data,
+        "lora",
+        StubScanner([model_data]),
+        str(model_dir),
+    )
+
+    assert success is True
+    entry = model_data["civitai"]["images"][0]
+    assert entry["type"] == "video"
+    assert (entry["width"], entry["height"]) == (1920, 1080)