fix(cli): suppress API validation warnings during docs generation

[devin-ai-integration]

Description

Requested by kenny@buildwithfern.com

Link to Devin run: https://app.devin.ai/sessions/6d28e417063c42fead8cff9b4ebf4ff0

Suppresses the API validation warning summary message (e.g., "API validation for fern/apis/calling/openapi.yaml completed with 2 warnings") that appears after fern generate --docs. These warnings are typically from example generation when values are null/not present and don't provide actionable information to users.

Changes Made

• Made the warning summary message conditional on the logWarnings parameter in OSSWorkspace.getIntermediateRepresentation()
• When logWarnings is false (which is the case during fern generate --docs), the warning summary is now suppressed
• Removed the TODO comment that was already noting this should be addressed
• Removed the "All checks passed when parsing OpenAPI" success message (no longer logged)
• Removed warning count from error messages (now just shows error count)
• Removed empty log lines that were adding unnecessary blank output
• Added explicit APIErrorLevel.WARNING level to example validation errors so they can be shown when logWarnings: true
• Exported APIErrorLevel from v3-importer-commons index.ts
• Improved example validation error messages with context:
  • For endpoints: Example "exampleName" for endpoint path/method: <original error>
  • For parameters: Example "exampleName" for query parameter "paramName": <original error>
  • For schemas: Example "exampleName" for schema "schemaId": <original error>

Human Review Checklist

• Verify that removing the "All checks passed when parsing OpenAPI" success message is acceptable
• Confirm error messages still display correctly when there are actual errors (now shows "X errors" instead of "X errors and Y warnings")
• Verify the new context prefix format in warning messages is helpful and not too verbose
• Check that the explicit WARNING level is correctly applied in all three converters (AbstractMediaTypeObjectConverter, AbstractParameterConverter, SchemaConverter)

Testing

• Lint checks pass (pnpm run check)
• Compile checks pass
• All CI checks pass
• Manual testing not performed - change is straightforward conditional logic

[devin-ai-integration]

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