[ Patch}: Add Z.ai provider with GLM-4.7 and GLM-4.5-Air models

[liveisgood]

Summary
Add Z.ai as a new provider with Anthropic-compatible GLM models (GLM-4.7 and GLM-4.5-Air).
What This Does

• Adds "zai" as a new ProviderId in type definitions
• Adds ZAI_API_KEY environment variable mapping
• Adds Z.ai provider to the model configuration
• Adds two GLM models to AVAILABLE_MODELS:
  • GLM-4.7 (Sonnet equivalent) - Flagship model
  • GLM-4.5-Air (Haiku equivalent) - Fast, cost-effective
• Updates runtime to handle Z.ai models with custom API endpoint
• Adds Z.ai icon and fallback provider to UI

How to Test

1. Add Z.ai API key in Settings
2. Select GLM-4.7 or GLM-4.5-Air model
3. Test with a simple prompt
   Technical Details

• Uses @langchain/anthropic ChatAnthropic with custom anthropicApiUrl
• Endpoint: https://api.z.ai/api/anthropic
• Follows existing provider/model patterns in the codebase
• No breaking changes to existing functionality
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zai-integration.patch

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• Z.ai docs: https://docs.z.ai/scenario-example/develop-tools/claude