dsh-commandcode-goat: Integrate Command Code Subscriptions as an llm-pi-ai Route

The DeepSeek Harness plugin dsh-commandcode-goat unifies Command Code's Go/GOAT/Pro/Max subscriptions under DSH's `llm-pi-ai` namespace, supporting single-credential management, web search, and usage display across multiple tiers. It is compatible with DSH >= 0.1.7-alpha.2, installs via the `link:` command, automatically syncs routing, and preserves user manual configuration. After installing and adding an API Key, all tiers can be managed uniformly in DSH.