Merge pull request 'feat(gateway): add Anthropic, OpenAI, Z.ai LLM providers (P8-002)' (#212) from feat/p8-002-llm-providers into main

Reviewed-on: mosaic/mosaic-stack#212

.env.example

@@ -62,9 +62,15 @@ OTEL_SERVICE_NAME=mosaic-gateway
 # Comma-separated list of Ollama model IDs to register (default: llama3.2,codellama,mistral)
 # OLLAMA_MODELS=llama3.2,codellama,mistral
 
-# OpenAI — required for embedding and log-summarization features
+# Anthropic (claude-sonnet-4-6, claude-opus-4-6, claude-haiku-4-5)
+# ANTHROPIC_API_KEY=sk-ant-...
+
+# OpenAI (gpt-4o, gpt-4o-mini, o3-mini)
 # OPENAI_API_KEY=sk-...
 
+# Z.ai / GLM (glm-4.5, glm-4.5-air, glm-4.5-flash)
+# ZAI_API_KEY=...
+
 # Custom providers — JSON array of provider configs
 # Format: [{"id":"<id>","baseUrl":"<url>","apiKey":"<key>","models":[{"id":"<model-id>","name":"<label>"}]}]
 # MOSAIC_CUSTOM_PROVIDERS=