Show the dataSync copy in a video, and answer its declaration

Play asks separately about FOREGROUND_SERVICE_DATA_SYNC: which use case, what
the service does, what the user loses if the task is deferred or interrupted,
and a video of the user triggering the work. The answers are now in section 5
of the release checklist, and the video is recorded.

The use case is Local processing -> Importing, exporting. Play's own chart
describes it as moving files from an SD card locally, which is what Paste and
Copy to... / Move to... do. The description (482/500 characters) names every
OperationKind - COPY, MOVE, DELETE, COMPRESS, EXTRACT - and states that the app
has no INTERNET permission, so network processing, backup/restore and media
transcoding are explicitly not ticked.

The video (18.0 s, captions burned in) shows a 1.8 GB synthetic folder copied to
another local folder: the selection and Copy, Paste here, the "Copying files"
notification with its progress bar, and the completed folder. It is cut from a
35.2 s raw take to remove the two waits; the target listing stays empty until
the copy completes, so those frames are progress rather than failure. The shade
was cleared of the phone's weather and Play cards first, leaving only Android's
generic USB cards, and every filename is synthetic.

Two traps are written down: do not press Up after Copy, because the selection
is already in AADemo and an extra Up makes Paste target AADemo ("Items already
exist here"); and open the shade only after cmd notification list shows the
app's notification, or the video shows no evidence of the service.

Verified: ./tools/verify.sh green, the code map current, links resolve, both
videos decode as H.264 1080x2400 with no audio, and the SRT has five cues.

docs/PLAY_RELEASE_CHECKLIST.md

@@ -174,6 +174,43 @@ honesty, not the justification.
       video field. The repository file is not a link, and a private video cannot be reviewed. What it
       shows, why the system UI is German, and how to re-shoot it: [PERMISSION_VIDEO](PERMISSION_VIDEO.md).
 
+### The foreground-service declaration (`dataSync`)
+
+`FileOpService` is a **`dataSync`** foreground service: it keeps a copy, move, delete (into the trash),
+compress or extract alive while the user is in another app, and mirrors the engine's progress into an
+ongoing, silent notification. It runs no network code and the app has no `INTERNET` permission. Play
+asks about this separately from All files access.
+
+- **Use case: Local processing → Importing, exporting.** Play's own chart describes the use case as
+  *"Includes migration of files from SD card. Show the user manually triggering an import or export
+  of files locally (for example, as moving files from an SD card)"* — which is what **Paste** and
+  **Copy to… / Move to…** do. Do **not** tick network processing, backing up/restoring, media
+  transcoding or "Other tasks": every `OperationKind` is local — `COPY`, `MOVE`, `DELETE`, `COMPRESS`,
+  `EXTRACT` — and none of them touches a network.
+
+- **Functionality description (482 / 500 characters, measured):**
+
+  ```
+  Plain Files is a file manager. Its dataSync service runs user-initiated local file operations: copying and moving files and folders between folders, internal storage, SD cards and USB drives; deleting into a 24-hour trash; creating ZIPs; extracting ZIP, TAR, GZ, BZ2, XZ and 7z archives. It keeps a long operation alive while the user switches apps and posts an ongoing, silent progress notification until the work ends. All operations are local; the app has no INTERNET permission.
+  ```
+
+- **If the task is deferred** (*"does not start immediately"*): *"If deferred, a copy, move, delete,
+  compress or extract the user just confirmed would not start while Plain Files is in the background:
+  no progress notification and no visible change until the app returns. A large operation could look
+  as if it had silently failed, and the user might start it again."*
+
+- **If the task is interrupted** (*"paused and/or restarted"*): *"If interrupted, the work stops.
+  Items already completed remain, but a file being copied or extracted can be left partly written at
+  the destination, and the user has to start the operation again. Nothing is overwritten without
+  asking, and deletes are staged in the 24-hour trash, so completed deletes remain recoverable."*
+
+- [ ] **Upload the foreground-service video.** `store-assets/video/fgs-import-export.mp4` (**18.0 s**,
+      captions burned in) to YouTube **Unlisted** or Drive with link sharing, then paste that URL into
+      the foreground-service declaration. It shows the selection, **Copy**, **Paste here**, the
+      **Copying files** notification with its progress bar, and the completed folder. It is a
+      different field from the All files access video. What was cut, the privacy checks, and how to
+      re-shoot it: [FGS_VIDEO](FGS_VIDEO.md).
+
 **Verify the shipped permission set** after every release build:
 
 ```bash