.NET Workflows - Update Declarative Integration Tests for File Cases

[crickman]

Motivation and Context

Refine test-cases around file input for declarative workfows.

Description

• Improve test validation
• Separate agent definitions
• Create appropriate agent for vision tests

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? If yes, add "[BREAKING]" prefix to the title of the PR.

[Copilot]

Pull request overview

This PR refines integration tests for declarative workflows by improving file input handling, separating agent definitions, and creating a dedicated vision agent for testing image and document processing capabilities.

Key Changes

• Created dedicated VisionAgentProvider for vision-based testing scenarios
• Refactored tests to support both image and PDF file types with parameterized test cases
• Enhanced test validation with improved assertions and output logging

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
MediaInput.yaml	Simplified workflow configuration by removing inline instructions and referencing dedicated VisionAgent
MediaInputTest.cs	Refactored tests from [Fact] to [Theory] to support multiple file types (images and PDFs) with parameterized data
VisionAgentProvider.cs	Added new agent provider specifically for vision/document analysis with appropriate instructions
TestAgentProvider.cs	Updated agent description to be more generic ("Basic agent") to reflect its general-purpose nature
AgentProvider.cs	Extended factory to support creation of VisionAgent through new Names.Vision constant