.NET: Rename Microsoft.Agents.AI.AzureAI to Microsoft.Agents.AI.Foundry and consolidate FoundryMemory (#5042)

* Update Foundry Responses as ChatClientAgent

* Migrate obsolete AzureAI integration tests to versioned agent pattern

Replace obsolete CreateAIAgentAsync/GetAIAgentAsync calls with
Agents.CreateAgentVersionAsync() + AsAIAgent(AgentVersion) in all
AzureAI integration tests.

- Rename AIProjectClient* test files to FoundryVersionedAgent*
- Register AIFunction tools in PromptAgentDefinition.Tools for
  server-side visibility via AsOpenAIResponseTool()
- Skip structured output tests (AzureAIProjectChatClient clears
  ResponseFormat for versioned agents)
- Remove all [Obsolete] attributes and #pragma warning disable CS0618

* Merge FoundryMemory package into AzureAI under Memory/ folder

Move all FoundryMemory source, unit tests, and integration tests into
the Microsoft.Agents.AI.AzureAI package. Change namespace from
Microsoft.Agents.AI.FoundryMemory to Microsoft.Agents.AI.AzureAI.

- Add [Experimental] to FoundryMemoryProviderOptions and Scope
- Rename internal AIProjectClientExtensions to MemoryStoreExtensions
- Update AzureAI .csproj with Compliance.Abstractions, Redaction
- Remove FoundryMemory from solution and release filter
- Update sample to reference AzureAI instead of FoundryMemory
- Delete old Microsoft.Agents.AI.FoundryMemory project and tests

* Add EnsureMemoryStoreCreatedAsync and memory existence checks to integration tests

- Ensure memory store is created before testing memory operations
- Add AZURE_AI_EMBEDDING_DEPLOYMENT_NAME config setting
- Assert memories exist in store via SearchMemoriesAsync before cleanup
- Verify scope isolation with direct memory store queries

* Fix and rename AzureAI unit tests for RAPI vs Versioned clarity

- Rename AsAIAgentAsync_* to AsAIAgent_* (drop Async from method group)
- Add _Rapi_ prefix to non-versioned (Responses API) tests
- Add _Versioned_ prefix to versioned agent tests where needed
- Fix RAPI tests: assert GetService<AIProjectClient>() is null
- Fix Versioned tests: assert IsType<FoundryAgent> and
  GetService<AIProjectClient>() returns the client instance
- Fix UserAgent header tests: proper HTTP handler routing
- Fix ChatClient_UsesDefaultConversationIdAsync test setup
- All 153 unit tests pass with 0 failures

* Rename Microsoft.Agents.AI.AzureAI to Microsoft.Agents.AI.Foundry

Rename the project, namespace, folder, and all references from
Microsoft.Agents.AI.AzureAI to Microsoft.Agents.AI.Foundry.
Also rename Workflows.Declarative.AzureAI to .Foundry.

- Rename src, unit test, integration test, and workflow folders
- Update namespaces in all source and test .cs files
- Update ProjectReferences in ~47 sample and test .csproj files
- Update solution files (.slnx, .slnf)
- Update sample using statements
- Update READMEs, SKILL.md, ADRs in docs/
- Disable package validation baseline for renamed packages
- Fix UTF-8 BOM encoding on all affected .cs files
- AzureAI.Persistent left completely unchanged

* Fix format: remove ImplicitUsings, add explicit usings, fix BOM encoding

- Remove ImplicitUsings=enable from Foundry csproj to resolve IDE0005
  on shared ReplacingRedactor.cs
- Add explicit System usings to all source files that relied on them
- Sort usings alphabetically per editorconfig rules
- Fix UTF-8 BOM on 12 sample Program.cs files
- Rename Azure AI Foundry Agents to Microsoft Foundry Agents in docs

dotnet/.github/skills/project-structure/SKILL.md

@@ -12,8 +12,8 @@ dotnet/
 │   ├── Microsoft.Agents.AI.Abstractions/         # Core AI agent abstractions
 │   ├── Microsoft.Agents.AI.A2A/                  # Agent-to-Agent (A2A) provider
 │   ├── Microsoft.Agents.AI.OpenAI/               # OpenAI provider
-│   ├── Microsoft.Agents.AI.AzureAI/              # Azure AI Foundry Agents (v2) provider
-│   ├── Microsoft.Agents.AI.AzureAI.Persistent/   # Legacy Azure AI Foundry Agents (v1) provider
+│   ├── Microsoft.Agents.AI.Foundry/               # Microsoft Foundry Agents (v2) provider
+│   ├── Microsoft.Agents.AI.AzureAI.Persistent/   # Legacy Microsoft Foundry Agents (v1) provider
 │   ├── Microsoft.Agents.AI.Anthropic/            # Anthropic provider
 │   ├── Microsoft.Agents.AI.Workflows/            # Workflow orchestration
 │   └── ...                                       # Other packages