Three fixes on top of the download progress feature:
1. Backend: Replace broken "no .incomplete = done" completion check
with a 95% byte threshold. HF downloads files sequentially, so
between files there are briefly no .incomplete files even though
the download is far from done (e.g. Kimi-K2.5 reported "done"
after downloading 22KB of config files out of 595GB).
2. Frontend: Track hasShownProgress flag. Only show "Download
complete. Loading into memory..." if we actually displayed
download progress before. For already-cached models where the
first poll returns progress=1.0, this avoids the misleading
"Download complete" message.
3. Frontend: Deduplicate recommended vs downloaded -- filter out
models already in the "Downloaded" section. Cache the fetched
lists at module level so re-mounting the popover does not flash
an empty "Downloaded" section.