Check-in [928524bd8c]

Review of a067c6e. JudgeFilled treated content.Expand's chain-bound error as a store fault and returned it, and DeltaStored failed storeDeltaContent with it.

A pusher could plant a dangling chain longer than maxDeltaChainDepth under a basis R, building it by re-rooting. After that, every honest push, pull or clone that supplied R as a delta failed for good.

Fix: - content now wraps its cycle and depth errors in ErrChainUnresolvable, and exports MaxDeltaChainDepth. - seedcheck counts ErrChainUnresolvable as unreadable, alongside a hash mismatch and a delta that does not apply or fails its checksum. Such a row is skipped and stays pending, so it stays withheld. - Real faults are still returned, such as content that does not decompress. - The classification uses errors.Is on the sentinel, so the expansion JudgeFilled already performs is not repeated.

Tests: - TestHorizonOverDeepPendingChainDoesNotBlockFill plants a pending row one node past the bound under R, then pushes R as a delta on a held basis. The push succeeds, R is stored and readable, and the over-deep row stays withheld. - TestUnresolvableChainSentinel pins the sentinel for a cycle and for a chain past the bound. - Dropping the classification, or either wrap, fails a test.

A cycle never reaches seedcheck: the receive pass's own basis-chain walk (receive_pass.go chainEnd) refuses it first. check-in: 8b946de415 user: [email protected] tags: main, trunk