v0.6.0 — X-Muninn-Prewarm: warm the cache without receiving the bytes
X-Muninn-Prewarm: warm the cache without receiving the bytes. 202 + job id, or
204 if already cached.
X-Muninn-Local-Only: answer from disk or 404, never contacting the Hub. All
three upstream call sites on the resolve path are suppressed, including ref
revalidation and the etag backfill on a hit -- not just the obvious miss.
Both together are a 400. They compose across requests: prewarm a set, then poll
with local-only to see what landed, with no management token and no upstream
request in the polling loop.