dsh-context-lens: View changes between adjacent model requests and cache reuse

dsh-context-lens is a pure observer plugin developed specifically for DeepSeek Harness, designed to continuously track and analyze context changes in real LLM requests within DSH sessions. By reading session logs (without injecting content or interfering with model calls), it generates a record for each request, displaying the submitted request context (such as model, system prompt, tool set, etc.) and cache reuse metrics, while automatically comparing differences with the previous request and alerting on potential drops. Its cache analysis is strictly based on the provider's `usage buckets` field to avoid inferring internal implementation. The plugin offers bilingual views (Chinese and English), retains the last 100 request records, emphasizes that "correlation does not imply causation," and explicitly does not guarantee determining the provider's internal cache key construction or harness.