fix image preview and add option for automatically stop auto screenshoting when idle

README.md

@@ -78,8 +78,14 @@ for anyone who wants to watch them.
 photo website does: the per-day counts arrive before any image does, so the
 scrollbar is honest about the album's real size from the first frame, and the
 thumbnails for a day are fetched only when you scroll near them. Click a photo to
-open it larger, Escape to go back. It is read-only — PhotoSync will not delete,
-move or favourite anything on your server.
+open it, Escape to go back. It is read-only — PhotoSync will not delete, move or
+favourite anything on your server.
+
+An opened photo is fetched at the largest size your server will serve — the
+original if it has full-size renditions enabled, its 1440px preview otherwise.
+The blur you see for the moment before it arrives is the thumbhash the timeline
+already carried, and it says so while it is standing in, so a blur is never
+mistaken for the photo.
 
 Videos in the album show their preview frame with a video badge in the corner.
 There is no playback; this is a screenshot mod.
@@ -98,6 +104,12 @@ puts it through the same queue as a manual one.
 - **Only while in a world** — on by default. No point photographing the main menu.
 - **Skip while a screen is open** — on by default. Your inventory is not a
   landscape.
+- **Skip if you have not moved** — on by default. A cycle is skipped when the
+  camera has been in the same place, looking the same way, for a whole interval:
+  that shot would be the previous one again. It resumes on its own the moment you
+  move or look somewhere else, so an afk stretch costs you one photo rather than
+  a hundred identical ones. The view is judged from the camera, so following
+  someone in spectator mode counts as moving.
 
 Automatic captures are recorded separately from manual ones, so the two are
 distinguishable everywhere they appear.
@@ -164,9 +176,14 @@ does not queue against a server it cannot reach, because the result is a list of
 failures you cannot act on.
 
 **Thumbnails are blank in Browse** — Minecraft's image decoder reads PNG and JPEG
-only, and Immich's default thumbnail format is WebP. PhotoSync detects this and
-switches to JPEG previews for the rest of the session, so this should self-correct
-after the first few tiles.
+only, and Immich's default thumbnail format is WebP. PhotoSync notices on the
+first tile and asks for JPEG previews instead for the rest of the session, so
+this self-corrects on its own.
+
+**An opened photo says it could not load** — close it and open it again, which
+retries. If it fails every time, the log line says why; the usual cause is
+Administration → Settings → Image → Preview format set to WebP on the server,
+which nothing on this side can decode. Set it to JPEG.
 
 **A jar refuses to load** — check the table above. Fabric enforces each jar's
 declared version range, so this means the jar is for a different bucket.