fix(downloads): a conversion's commit, a stopped upload, the fast join and a clip's copy hold up

- The fast join gives each ffconcat entry its own media-only format whitelist, so a library file
  can no longer be opened as a nested concat list (the list's whitelist was handed down to it).
- A file the guarded probe cannot read is a download-only file, not a guess from yt-dlp's info.
- A conversion's or an ingest's commit that raises is re-read in a fresh session before any file
  is removed: a commit that landed keeps the file its row now names.
- An original that cannot be removed after conversion is logged; the upload stays ready.
- An upload whose conversion is cancelled or deleted midway is freed once nothing holds it; a
  paused one is kept.
- A shared link says "preparing" only while its video's job is queued or running.
- The admin storage view counts every file on disk ("Files on disk"), not only ready ones.
- A clip's failure title, unknown failure and cancel dialog, and a clip's and an upload's delete
  dialog speak of what the job made; an upload's quota refusal explains that the original is kept.
- /watch announces "preparing" as an alert and moves focus to the new Retry after an action.

frontend/src/components/useDownloadActions.tsx

@@ -16,7 +16,7 @@ import {
   Trash2,
 } from "lucide-react";
 import { qk } from "../lib/queryKeys";
-import { api, type DownloadJob } from "../lib/api";
+import { api, type DownloadJob, type DownloadJobKind } from "../lib/api";
 import { notifyActionError } from "../lib/actionErrors";
 import { invalidateDownloads, quickShareLink } from "../lib/downloads";
 import { libraryRowActions, sharedRowActions } from "../lib/downloadActions";
@@ -46,6 +46,29 @@ const CANCEL_UPLOAD = {
   body: "downloads.confirm.cancelUploadBody",
   action: "downloads.confirm.cancelUploadAction",
 };
+const CANCEL_EDIT = {
+  title: "downloads.confirm.cancelEditTitle",
+  body: "downloads.confirm.cancelEditBody",
+  action: "downloads.confirm.cancelEditAction",
+};
+// Cancelling an upload deletes the file it uploaded (there is nothing to fetch again), so its
+// confirmation says so — "stop the download" would read as safe to undo. A clip is being cut, not
+// downloaded.
+const CANCEL_COPY: Record<DownloadJobKind, typeof CANCEL_DOWNLOAD> = {
+  download: CANCEL_DOWNLOAD,
+  upload: CANCEL_UPLOAD,
+  edit: CANCEL_EDIT,
+};
+// Deleting a download may leave its shared cache file for other holders. An upload and a clip are
+// their owner's alone (a clip's asset is keyed by its user), so deleting one removes the file for good.
+const DELETE_COPY: Record<DownloadJobKind, { title: string; body: string }> = {
+  download: { title: "downloads.confirm.deleteTitle", body: "downloads.confirm.deleteBody" },
+  upload: {
+    title: "downloads.confirm.deleteUploadTitle",
+    body: "downloads.confirm.deleteUploadBody",
+  },
+  edit: { title: "downloads.confirm.deleteEditTitle", body: "downloads.confirm.deleteEditBody" },
+};
 
 export function useDownloadActions({
   onPlay,
@@ -159,10 +182,8 @@ export function useDownloadActions({
           label: t("downloads.actions.cancel"),
           icon: icon(Ban),
           danger: true,
-          // Cancelling an upload deletes the file it uploaded (there is nothing to fetch again), so
-          // its confirmation says so — "stop the download" would read as safe to undo.
           onSelect: () => {
-            const copy = job.job_kind === "upload" ? CANCEL_UPLOAD : CANCEL_DOWNLOAD;
+            const copy = CANCEL_COPY[job.job_kind ?? "download"];
             void confirmThen(t(copy.title), t(copy.body), t(copy.action), () =>
               act.mutate({ id: job.id, op: "cancel" }),
             );
@@ -233,13 +254,12 @@ export function useDownloadActions({
           label: t("downloads.actions.delete"),
           icon: icon(Trash2),
           danger: true,
-          onSelect: () =>
-            void confirmThen(
-              t("downloads.confirm.deleteTitle"),
-              t("downloads.confirm.deleteBody"),
-              t("downloads.actions.delete"),
-              () => act.mutate({ id: job.id, op: "delete" }),
-            ),
+          onSelect: () => {
+            const copy = DELETE_COPY[job.job_kind ?? "download"];
+            void confirmThen(t(copy.title), t(copy.body), t("downloads.actions.delete"), () =>
+              act.mutate({ id: job.id, op: "delete" }),
+            );
+          },
         },
       ],
     );