Pulls in fixes from two libfossil releases:

- v0.4.4 (libfossil#14): hub xfer handler no longer panics with "content.MakePublic: rid must be positive" when a client cancels mid-transfer. Affects EdgeSync hubs that serve concurrent clones.

- v0.4.5 (libfossil#17, libfossil#18): sync.Clone now converges against a hub being written to during the clone session. Three compounding root causes fixed: server-side rid cap (snapshot via CookieCard), client-side CloneSeqNoCard cursor emission, and cookie roundtrip. Wire-format compatible with older peers.

No EdgeSync source changes required — both fixes are libfossil-internal.

Closes #86. leaf check-in: 6c16b3e646 user: [email protected] tags: trunk, chore/bump-libfossil-v0.4.5