fix(downloads): a download larger than the space left says so, not "processing failed"

yt-dlp refuses a file announced over `max_filesize` by logging one line and returning with no file
(measured, and pinned in test_formats against a local server): the worker found no output and
failed the job as `postprocess`. `formats.watching_size_cap` now sees that line through our yt-dlp
logger, and the download (and, should it ever happen, a YouTube clip's range fetch) fails as the
owner's refusal with DOWNLOAD_TOO_BIG_MESSAGE, classified `quota_exceeded`. The download's quota
copy says it does not fit in what is left — true at a full cap too — instead of "Storage full".
A pre-existing type error the change touched is fixed (baseline down by one).

backend/app/downloads/pipeline.py

@@ -535,8 +535,8 @@ def _download(
         # free space, which is what the `quota_exceeded` category tells them.
         if remaining_bytes == 0:
             raise _OwnerRefused(dlerrors.QUOTA_FULL_MESSAGE)
-        info = _media_info(
-            _extract_with_fallback(
+        with formats.watching_size_cap() as over_cap:
+            fetched = _extract_with_fallback(
                 job_id,
                 asset_id,
                 url,
@@ -546,7 +546,11 @@ def _download(
                 cookiefile=str(cookiefile) if cookiefile else None,
                 max_bytes=remaining_bytes,
             )
-        )
+        info = _media_info(dict(fetched))
+        # yt-dlp refused a file larger than what is left: it returns with no file, which would
+        # otherwise read as a processing fault. The owner's storage, so the owner's refusal.
+        if over_cap[0]:
+            raise _OwnerRefused(dlerrors.DOWNLOAD_TOO_BIG_MESSAGE)
         # Re-resolve now that yt-dlp's info reveals the true source (a bare/redirected url only
         # identifies post-extraction) so the .nfo uniqueid type + uploader_url agree on one source.
         adapter = adapters.resolve_adapter(source_kind, source_ref, info)
@@ -959,17 +963,21 @@ def _clip_source(
                 )
         _set_job(job_id, phase="downloading", progress=0)
         try:
-            info = _extract_with_fallback(
-                job_id,
-                asset_id,
-                url,
-                formats.normalize(clipmod.YOUTUBE_FETCH_SPEC),
-                staging,
-                adapters.resolve_adapter("youtube", spec["ref"]),
-                cookiefile=str(cookiefile) if cookiefile else None,
-                max_bytes=remaining,
-                section=(spec["start_s"], spec["end_s"]),
-            )
+            with formats.watching_size_cap() as over_cap:
+                info = _extract_with_fallback(
+                    job_id,
+                    asset_id,
+                    url,
+                    formats.normalize(clipmod.YOUTUBE_FETCH_SPEC),
+                    staging,
+                    adapters.resolve_adapter("youtube", spec["ref"]),
+                    cookiefile=str(cookiefile) if cookiefile else None,
+                    max_bytes=remaining,
+                    section=(spec["start_s"], spec["end_s"]),
+                )
+            # Should yt-dlp's own cap ever refuse the range (see `_download`): the owner's storage.
+            if over_cap[0]:
+                raise _OwnerRefused(dlerrors.CLIP_TOO_BIG_MESSAGE)
         except (_Aborted, _OwnerRefused):
             raise
         except Exception as exc:  # re-raised below with the download catalog's diagnosis