Old ComfyUI_frontend releases pulled in via --front-end-version
<repo>@latest were never removed, causing web_custom_versions/ to
grow unbounded (one user reported 5.11 GB).
When the user requests an auto-resolving specifier (@latest or
@prerelease), record which concrete version was materialized in a
small .auto_managed.json next to the per-provider folders. On a
subsequent auto-managed run, prune any previously-tracked folder
that is no longer the current one. Explicitly pinned versions
(e.g. @v1.46.0) are left alone, and if a user explicitly pins a
version that had previously been downloaded under @latest, it is
promoted out of the auto-managed set so it survives future cleanup.
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