.NET: Adding default providers and tools to HarnessAgent

[westey-m]

Motivation and Context

We want the HarnessAgent to come with a set of default tools. Adding a set of providers and tools to the HarnessAgent to allow it to do a lot of work out of the box, with opt-outs for each feature.

Description

• Adding default providers and tools to HarnessAgent
• Adding overridable harness instructions (separate from agent instructions)
• Update samples to use features as needed.

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

Adds default HarnessAgent capabilities so agents get common providers, tools, and decorators out of the box, with options to opt out and separate harness-level instructions from agent-specific instructions.

Changes:

• Adds default ToolApproval, OpenTelemetry, WebSearch, Todo, AgentMode, FileMemory, FileAccess, and AgentSkills configuration to HarnessAgent.
• Adds HarnessAgentOptions switches and custom store/source options for those defaults.
• Updates harness samples and unit tests to reflect the new default behavior.

Reviewed changes

Copilot reviewed 12 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
dotnet/src/Microsoft.Agents.AI.Harness/HarnessAgent.cs	Builds default agent decorators, tools, context providers, and instruction composition.
dotnet/src/Microsoft.Agents.AI.Harness/HarnessAgentOptions.cs	Adds opt-out flags and customization properties for default harness features.
dotnet/src/Microsoft.Agents.AI/Harness/AgentMode/AgentModeProvider.cs	Expands default plan/execute mode instructions and formatting.
dotnet/src/Microsoft.Agents.AI/Harness/FileMemory/FileMemoryProvider.cs	Refines memory guidance text.
dotnet/src/Microsoft.Agents.AI/Harness/Todo/TodoProvider.cs	Refines todo guidance text.
dotnet/tests/Microsoft.Agents.AI.Harness.UnitTests/HarnessAgentTests.cs	Updates existing tests and adds coverage for default feature inclusion/exclusion.
dotnet/tests/Microsoft.Agents.AI.Harness.UnitTests/HarnessAgentOptionsTests.cs	Adds option default and set/get coverage for new properties.
dotnet/samples/02-agents/Harness/Harness_Step01_Research/Program.cs	Simplifies research sample to rely on new HarnessAgent defaults.
dotnet/samples/02-agents/Harness/Harness_Step02_Research_WithSubAgents/Program.cs	Updates sub-agent sample to use built-in web search and disable unused defaults.
dotnet/samples/02-agents/Harness/Harness_Step03_DataProcessing/Program.cs	Updates data processing sample to rely on default file access.
dotnet/samples/02-agents/Harness/Harness_Step03_DataProcessing/README.md	Documents the updated default file access behavior and sample data location.
dotnet/samples/02-agents/Harness/Harness_Step03_DataProcessing/Harness_Step03_DataProcessing.csproj	Removes old sample data copy item.
dotnet/samples/02-agents/Harness/Harness_Step03_DataProcessing/working/sales.csv	Adds sample CSV data under the default working folder.

Comments suppressed due to low confidence (1)

dotnet/src/Microsoft.Agents.AI/Harness/AgentMode/AgentModeProvider.cs:91

• Use the American English spelling "judgment" here for consistency with the repository's documentation style.

            2. Work autonomously — use your best judgement to make decisions and keep progressing without asking the user questions. The goal is to have a complete, useful result ready when the user returns.

[github-actions]

Automated Code Review

Reviewers: 4 | Confidence: 91% | Result: All clear

Reviewed: Correctness, Security Reliability, Test Coverage, Design Approach

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Automated review by westey-m's agents