.NET: Add SkillExecutor.HostedCodeInterpreter() skill script execution mode

[SergeyMenshykh]

Summary

Add support for executing agent skill scripts via the LLM's hosted code interpreter, encapsulated as SkillExecutor.HostedCodeInterpreter().

Changes

• Introduce SkillScriptExecutor abstract class with GetInstructions() and GetTools() methods
• Add HostedCodeInterpreterExecutor sealed subclass returned by SkillScriptExecutor.HostedCodeInterpreter()
• Register HostedCodeInterpreterTool when executor is enabled
• FileAgentSkillsProvider script execution is off by default; enabled via FileAgentSkillsProviderOptions.Executor
• Improve DefaultSkillsInstructionPrompt to instruct LLMs to use full resource paths with read_skill_resource
• Add Agent_Step02_ScriptExecutionWithCodeInterpreter sample project

Closes #4131

[Copilot]

Pull request overview

This pull request introduces support for executing agent skill scripts via the LLM's hosted code interpreter. The implementation adds a new SkillScriptExecutor abstraction with a concrete HostedCodeInterpreterExecutor implementation that integrates with FileAgentSkillsProvider. The PR also enhances skill resource path detection to support backtick-quoted paths in addition to markdown links, and includes a comprehensive sample demonstrating password generation via script execution.

Changes:

• Introduced SkillScriptExecutor abstract class with factory method pattern for extensibility
• Added HostedCodeInterpreterExecutor that provides instructions and registers HostedCodeInterpreterTool
• Enhanced FileAgentSkillsProvider to optionally enable script execution via FileAgentSkillsProviderOptions.Executor
• Migrated prompt templating from format strings ({0}) to named placeholders ({skills}, {executor_instructions})
• Updated regex pattern to recognize backtick-quoted resource paths alongside markdown links
• Added comprehensive unit tests and Agent_Step02_ScriptExecutionWithCodeInterpreter sample project

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
dotnet/src/Microsoft.Agents.AI/Skills/SkillScriptExecutor.cs	Abstract base class defining the contract for script execution modes with factory method
dotnet/src/Microsoft.Agents.AI/Skills/HostedCodeInterpreterExecutor.cs	Concrete implementation providing instructions and tools for hosted code interpreter execution
dotnet/src/Microsoft.Agents.AI/Skills/FileAgentSkillsProviderOptions.cs	Added Executor property to enable optional script execution
dotnet/src/Microsoft.Agents.AI/Skills/FileAgentSkillsProvider.cs	Integrated executor instructions and tools; migrated to named placeholder templating
dotnet/src/Microsoft.Agents.AI/Skills/FileAgentSkillLoader.cs	Enhanced regex to detect backtick-quoted resource paths (e.g., `scripts/run.py`)
dotnet/tests/Microsoft.Agents.AI.UnitTests/AgentSkills/SkillScriptExecutorTests.cs	Comprehensive tests for executor creation, instruction/tool provisioning, and provider integration
dotnet/tests/Microsoft.Agents.AI.UnitTests/AgentSkills/FileAgentSkillsProviderTests.cs	Updated custom template test to use named placeholders; removed obsolete format validation test
dotnet/tests/Microsoft.Agents.AI.UnitTests/AgentSkills/FileAgentSkillLoaderTests.cs	Tests for backtick resource path extraction in single and mixed scenarios
dotnet/samples/.../Agent_Step02_ScriptExecutionWithCodeInterpreter/	Complete sample demonstrating script execution with password-generator skill
dotnet/agent-framework-dotnet.slnx	Added new sample project to solution
dotnet/samples/GettingStarted/AgentSkills/README.md	Updated to reference new Step02 sample