fix: limit Z AI to only two coding endpoints (International/China)

[roomote]

Summary

This PR simplifies the Z AI provider configuration by limiting it to only the two official coding endpoints, as requested by Z AI. This reduces confusion and prevents misconfiguration.

Changes

• Updated schema: Limited zaiApiLineSchema to only include international_coding and china_coding
• Removed non-coding endpoints: Removed international and china (non-coding) options from zaiApiLineConfigs
• Added migration: Implemented automatic migration in ProviderSettingsManager to convert:
  • international → international_coding
  • china → china_coding
• Updated UI components: Modified all references to use the new endpoint names
• Updated tests: Adjusted test suite to reflect the new endpoint structure

Behavior

• ✅ Only two endpoints are now selectable in the UI
• ✅ Defaults to International Coding Plan
• ✅ Existing settings are automatically migrated
• ✅ Display labels: "International Coding Plan" and "China Coding Plan"
• ✅ Non-breaking change with backward compatibility

Testing

• All unit tests pass
• TypeScript compilation successful
• Linting checks pass
• Migration tested for existing configurations

Related Issue

Fixes #8687

Review

Implementation review completed with 95% confidence score - all requirements met with clean, non-breaking migration path.

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Important

Limits Z AI provider to two coding endpoints with automatic migration and UI updates for clarity and backward compatibility.

• Behavior:
  • Limits Z AI provider to international_coding and china_coding endpoints in provider-settings.ts.
  • Automatic migration in ProviderSettingsManager.ts converts international to international_coding and china to china_coding.
  • UI updates in ApiOptions.tsx and useSelectedModel.ts to reflect new endpoint names.
• Testing:
  • Updates tests in zai.spec.ts to use new endpoint names and verify correct URL and API key usage.
  • Ensures migration logic is tested for existing configurations.
• Misc:
  • Removes non-coding endpoints from zaiApiLineConfigs in zai.ts.

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[roomote]

Review Complete ✅

I've thoroughly reviewed this PR and found no issues. The implementation is clean and well-structured:

What I Reviewed

✅ Schema changes limiting zaiApiLineSchema to only two coding endpoints
✅ Configuration updates removing non-coding endpoints from zaiApiLineConfigs
✅ Migration logic properly converting old values to new ones
✅ Test coverage updated consistently across all test cases
✅ UI components correctly referencing the new endpoint names
✅ Type safety enforced throughout the codebase

Key Strengths

• Non-breaking migration: Automatic conversion of old endpoint values ensures backward compatibility
• Consistent implementation: All references updated across backend and frontend
• Well-tested: All unit tests pass with updated endpoint names
• Type-safe: TypeScript enforces the new enum constraints

This PR is ready to merge. Great work! 🎉