dsh-deadend: A Failure Ledger and Automatic Invalidation Mechanism for Coding Agents

The DeepSeek Harness plugin `dsh-deadend` is designed for coding agents to address the problem of repeatedly attempting known failing approaches. By recording approaches that have been tried and found infeasible, and validating them before any future attempt, it turns failure experience into lasting repository assets. The plugin includes core features such as anchor tracking, automatic expiration, and command normalization, and stores its data in the repository rather than locally to support multi-user collaboration. Once installed and enabled, agents can use commands such as `check` and `record` to efficiently manage failure records and avoid repeating ineffective work.