Derived clips: link MP4 versions, list them apart, video Enhance output

Groundwork for Enhance "Animate" (#208): a video made from a photo.

- Version linking reads the XMP link from MP4 / MOV too (top-level uuid box
  with the XMP UUID, mdat seeked over), at ingest and on Enhance approve.
- New kind `animated`, a derived clip (CLIP_KINDS): hidden behind the photo
  like a version, but not counted in photo_version_counts / version_count,
  never a display choice (400 clip_not_displayable), and listed as `clips`
  in GET /image/versions. Approve returns the clip entry.
- Templates whose imageapi:save is ImageApiSaveVideoVersion report
  output "video" in /enhance/templates (no enhance.toml change). Previews
  already relay ComfyUI's content type (video/mp4).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/versions/integration_tests.rs

@@ -14,7 +14,7 @@ use diesel::sql_query;
 use diesel::sql_types::{BigInt, Text};
 use diesel::sqlite::SqliteConnection;
 
-use super::xmp::test_png::{producer_xmp, write_png};
+use super::xmp::test_png::{mp4_bytes, producer_xmp, write_png};
 use super::*;
 use crate::data::Claims;
 use crate::database::test::in_memory_db_connection;
@@ -782,6 +782,49 @@ async fn display_choice_set_from_a_version_path_cleared_and_validated() {
     assert_eq!(awtest::call_service(&app, req).await.status(), 200);
 }
 
+#[actix_rt::test]
+async fn an_animated_clip_links_hides_and_is_listed_apart_from_versions() {
+    let fx = fx();
+    let original = fx.put("2014/IMG_1.JPG", b"photo bytes");
+    let rel = "2014/aiedits/IMG_1.JPG.animated.mp4";
+    let clip = fx.put(
+        rel,
+        &mp4_bytes(Some(&producer_xmp(&original, "animated", &[])), 3),
+    );
+    let files = vec![(fx.root.join(rel), rel.to_string())];
+    assert_eq!(
+        link_new_files(&fx.library, &files, &fx.exif_arc(), &fx.state.version_dao),
+        1
+    );
+    let app = photos_app!(fx);
+
+    // Hidden behind the photo, like a version, and not counted as one.
+    let (_, body) = get_json!(app, "/photos?path=&recursive=true&sort=nameasc");
+    assert_eq!(body["photos"], serde_json::json!(["2014/IMG_1.JPG"]));
+    assert!(body.get("photo_version_counts").is_none(), "{body}");
+
+    // Listed under `clips`, from the photo's path or the clip's own.
+    for path in ["2014/IMG_1.JPG", rel] {
+        let (status, body) = get_json!(app, &format!("/image/versions?path={path}"));
+        assert_eq!(status, 200);
+        assert_eq!(body["versions"], serde_json::json!([]));
+        assert_eq!(body["clips"][0]["hash"], clip);
+        assert_eq!(body["clips"][0]["kind"], "animated");
+        assert_eq!(body["clips"][0]["path"], rel);
+    }
+
+    // Never the photo's display version.
+    let req = awtest::TestRequest::put()
+        .uri("/image/versions/display")
+        .insert_header(("Authorization", format!("Bearer {}", Fx::token())))
+        .set_json(serde_json::json!({"path": "2014/IMG_1.JPG", "display_hash": clip}))
+        .to_request();
+    let resp = awtest::call_service(&app, req).await;
+    assert_eq!(resp.status(), 400);
+    let body: serde_json::Value = awtest::read_body_json(resp).await;
+    assert_eq!(body["code"], "clip_not_displayable");
+}
+
 #[actix_rt::test]
 async fn deleting_the_displayed_version_falls_back_to_the_original() {
     let (fx, _o, v1, _v2) = seeded();