Add daemon restart, preview diagnostics, browse caching, and rate-limit pauses

docs/media-scraper.md

@@ -157,6 +157,25 @@ Previews run after every walk:
   (`VESKSLOP_MEDIA_PREVIEW_BATCH`, `VESKSLOP_MEDIA_PREVIEW_BATCH_PAUSE_MS`), because bursts of
   thumbnail fetches trigger Discord and provider rate limits. A batch counts rows, not successes.
 
+## Rate limits
+
+Discord and the provider APIs throttle bursts. The engine detects limiting and holds all media
+traffic:
+
+- A `429` from a preview or download fetch pauses the pass; the row stays pending (never marked as a
+  permanent error) and is retried later.
+- A walk page that fails with a `429` or a rate-limit message registers a cooldown, and every page
+  and preview waits it out before continuing.
+- The pause is `VESKSLOP_MEDIA_RATELIMIT_PAUSE_MS` (default 60 s), or the server's `Retry-After`
+  when it is longer. Detection is logged as `rate limit detected; pausing media traffic until …`.
+
+## Browsing cache
+
+Browsing never calls Discord. The grid renders cached previews or local files only; videos without
+a cached still show a labeled placeholder, and playback streams only when the user presses play.
+GIF hover plays the animated GIF cached in `thumbs/` (the original is kept alongside the static
+frame and referenced by `anim_hash`), never the provider, so scrolling cannot spam anyone.
+
 ## Job states
 
 `queued`, `running`, `paused`, `stopping`, `done`, `failed`, `pending-delete`, `deleting`, `deleted`.