[CT-80] ownership_chain module has no test for a broken or circular chain

[mftee]

Overview

contract/src/module/ownership_chain/mod.rs (212 lines) presumably builds the transfer history for a document, but has no evident test for a malformed chain — e.g. a transfer record pointing to a previous-owner entry that doesn't exist, or (in a corrupted-data scenario) a cycle — which should be detected rather than causing an infinite loop or silent truncation.

Tasks

• Add validation that detects a broken link (missing previous-owner reference) or a cycle when building the chain
• Add a test constructing a deliberately broken chain and asserting it's detected rather than looping or truncating silently

Acceptance Criteria

• Building an ownership chain over corrupted/circular data returns a clear error instead of hanging or truncating silently

Notes for Contributors

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