docs: record that the Gitea link answers range requests, so the video seeks

docs/PLAY_RELEASE_CHECKLIST.md

@@ -292,9 +292,12 @@ action except the items marked **[code]**.
          Checked from outside this network: **200**, `Content-Type: video/mp4`,
          `Content-Length: 1847900` and `Content-Disposition: inline`, so a reviewer's browser plays
          it in the tab rather than prompting a download, and the served bytes are identical to the
-         recording (sha256 match). Two things to know before pasting: the URL is pinned to `main`,
-         so a re-shoot has to **overwrite the file in place** rather than be added alongside it; and
-         replacing the video at all means resubmitting the declaration.
+         recording (sha256 match). A `Range: bytes=0-99` request answers **206** with exactly those
+         100 bytes even though `Accept-Ranges` is not advertised, so seeking works and a player can
+         start without fetching the whole file first — which matters here because `screenrecord`
+         writes the `moov` atom at the very end of the file. Two things to know before pasting: the
+         URL is pinned to `main`, so a re-shoot has to **overwrite the file in place** rather than
+         be added alongside it; and replacing the video at all means resubmitting the declaration.
          (An unlisted YouTube upload of the same file works equally well if a link that survives
          future commits is preferred — but then it is a second place to keep in step.)