DeepSeek Harness Reasoning Level Auto-Selection Plugin

The `dsh-plugin-jev-effort-selector` plugin uses the Jev System One model to automatically assess message complexity, enabling intelligent derivation of DeepSeek Harness reasoning levels. It reads model-declared levels, uses the context envelope to determine task continuity, and ensures unfinished tasks are not set below the previous tier. With session isolation, manual-selection priority, and silent fallback on failure, it addresses the inefficiency and forgetfulness of manual switching, making it suitable for DSH users who need fine-grained control over reasoning costs.