Add llm-zai and llm-zenmux to plugin directory

[ShellLM]

Adds two new plugins to the Remote APIs section of the plugin directory:

• llm-zai — supports Z.AI's GLM models (glm-5.2, glm-5.1, glm-5, glm-5-turbo, vision variants) plus Coding Plan endpoints, with thinking-effort levels and preserved/interleaved reasoning. Published: https://pypi.org/project/llm-zai/
• llm-zenmux — access to models hosted on ZenMux via their OpenAI Chat Completions and Anthropic Messages APIs, with live model-list discovery. Published: https://pypi.org/project/llm-zenmux/

Both require llm>=0.32a0 (use the llm 0.32 Prompt/Message API and StreamEvent reasoning support).