.NET: docs/workflow fileinput sample dotnet

[Vincent Biret (baywet)]

fixes #2772

[github-actions]

MAF Automated Review — Iteration 1

Result: No findings
Scope: full PR (2 commit(s)): c4d0259974e6, bc0eb76c8062
Model: gpt-5.6-sol

Overview

This PR adds a declarative workflow sample that uploads a local file, supplies it as HostedFileContent in a ChatMessage, and cleans up the uploaded file after execution. The shared runner overload delegates to the existing execution path, while the declarative root explicitly accepts ChatMessage inputs and existing integration coverage uses the same upload purpose. No publishable Critical, High, or Medium defect remains after reconciling the proposed failure modes against those guards.

Reviewed the supplied pull-request change set across correctness, security/reliability, architecture, and failure behavior.
No publishable findings remained after source verification for this scope.

[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated no new comments.

Suppressed comments (1)

dotnet/samples/03-workflows/Declarative/FileInput/Program.cs:63

• The sample uploads ProductBrief.txt, but this definition creates an agent with no tool that can read it. Foundry Responses direct file input supports PDFs, while .txt is supported through Code Interpreter; without that tool, the default dotnet run path cannot produce the advertised summary. Enable Code Interpreter with an automatic container so the file already present in the model input is made available to the agent.

    private static DeclarativeAgentDefinition DefineFileInputAgent(IConfiguration configuration) =>
        new(configuration.GetValue(Application.Settings.FoundryModel))
        {
            Instructions =