.NET: Revert ".NET: Support hosted code interpreter for skill script execution"

[SergeyMenshykh]

Reverts #4192 until there's further clarity regarding the design of script executors.

[Copilot]

Pull request overview

Reverts the earlier .NET “hosted code interpreter” script-execution support for Agent Skills while keeping the core file-based skills provider behavior.

Changes:

• Removes hosted code interpreter script-execution types, options, tests, and the Step02 sample.
• Updates FileAgentSkillsProvider to use composite-format ({0}) prompt templating and adds validation for custom templates.
• Renames/internalizes some skills-loading implementation types (frontmatter/skill/loader) consistent with the revert.

Reviewed changes

Copilot reviewed 22 out of 22 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
dotnet/tests/Microsoft.Agents.AI.UnitTests/AgentSkills/HostedCodeInterpreterFileAgentSkillScriptExecutorTests.cs	Removes tests for the hosted code interpreter script executor.
dotnet/tests/Microsoft.Agents.AI.UnitTests/AgentSkills/FileAgentSkillsProviderTests.cs	Switches custom prompt template placeholder to {0} and adds invalid-template constructor test.
dotnet/tests/Microsoft.Agents.AI.UnitTests/AgentSkills/FileAgentSkillScriptExecutorTests.cs	Removes integration tests for script executor wiring into the provider.
dotnet/tests/Microsoft.Agents.AI.UnitTests/AgentSkills/FileAgentSkillLoaderTests.cs	Updates frontmatter type usage and removes tests tied to the reverted resource parsing behavior.
dotnet/src/Microsoft.Agents.AI/Skills/SkillFrontmatter.cs	Renames/replaces the prior frontmatter type with an internal SkillFrontmatter.
dotnet/src/Microsoft.Agents.AI/Skills/HostedCodeInterpreterFileAgentSkillScriptExecutor.cs	Removes hosted code interpreter executor implementation.
dotnet/src/Microsoft.Agents.AI/Skills/FileAgentSkillsProviderOptions.cs	Removes script-executor option and documents {0} placeholder format.
dotnet/src/Microsoft.Agents.AI/Skills/FileAgentSkillsProvider.cs	Removes executor/tool merging logic; updates default prompt template and custom template handling.
dotnet/src/Microsoft.Agents.AI/Skills/FileAgentSkillScriptExecutor.cs	Removes script executor abstraction.
dotnet/src/Microsoft.Agents.AI/Skills/FileAgentSkillScriptExecutionDetails.cs	Removes script execution details model.
dotnet/src/Microsoft.Agents.AI/Skills/FileAgentSkillScriptExecutionContext.cs	Removes script execution context model.
dotnet/src/Microsoft.Agents.AI/Skills/FileAgentSkillLoader.cs	Internalizes loader, adjusts resource link regex, and internalizes resource read API.
dotnet/src/Microsoft.Agents.AI/Skills/FileAgentSkill.cs	Internalizes the skill model and updates it to use SkillFrontmatter.
dotnet/samples/02-agents/AgentSkills/README.md	Removes reference to the reverted Step02 sample.
dotnet/samples/02-agents/AgentSkills/Agent_Step02_ScriptExecutionWithCodeInterpreter/skills/password-generator/scripts/generate.py	Deletes script resource from the removed Step02 sample.
dotnet/samples/02-agents/AgentSkills/Agent_Step02_ScriptExecutionWithCodeInterpreter/skills/password-generator/references/PASSWORD_GUIDELINES.md	Deletes reference doc from the removed Step02 sample.
dotnet/samples/02-agents/AgentSkills/Agent_Step02_ScriptExecutionWithCodeInterpreter/skills/password-generator/SKILL.md	Deletes the sample skill definition for the removed Step02 sample.
dotnet/samples/02-agents/AgentSkills/Agent_Step02_ScriptExecutionWithCodeInterpreter/README.md	Deletes Step02 sample documentation.
dotnet/samples/02-agents/AgentSkills/Agent_Step02_ScriptExecutionWithCodeInterpreter/Program.cs	Deletes Step02 sample program.
dotnet/samples/02-agents/AgentSkills/Agent_Step02_ScriptExecutionWithCodeInterpreter/Agent_Step02_ScriptExecutionWithCodeInterpreter.csproj	Deletes Step02 sample project.
dotnet/samples/02-agents/AgentSkills/Agent_Step01_BasicSkills/Program.cs	Removes a warning comment block from the sample.
dotnet/agent-framework-dotnet.slnx	Removes Step02 sample project reference from the solution.