dsh-surface-contract-proof: Recording fixed semantic contracts for DSH surface

dsh-surface-contract-proof is an MIT-licensed DSH plugin designed to verify whether the three types of machine communication surfaces—DSH ToolRuntime, MCP JSON-RPC, and CLI JSON—adhere to fixed semantic contracts. Based on explicit SHA-256-fixed JSON fixtures, the plugin ensures consistency by calculating canonical digests, thereby avoiding side effects or credential risks associated with directly replaying requests. Its core functions include `inspect` (to generate a baseline digest) and `verify` (to validate the current state), providing DSH tools and MCP aliases. The plugin adopts a fail-closed strategy, rejecting access when data is missing, expired, or malformed, and...