dsh-shipgate: Local-First DSH Pre-Merge Delivery Receipt Generator

dsh-shipgate is a local-first pre-merge delivery proof generation plugin for DeepSeek Harness (DSH). It reuses the local inspect core and registers the `shipgate_inspect` tool in the DSH environment. The solution supports command-line or Harness tool invocation, can generate receipts and verify inspection results, but does not execute inspection logic or upload source code. Users should generate advisory proofs locally; to apply project failure policies, set `ci: true`.