Upgrade NuGet dependencies to latest compatible versions

[BenjaminMichaelis]

Overview

Updates all production NuGet dependencies to their latest stable and preview releases. This captures recent improvements, features, and security updates across the dependency tree while maintaining compatibility with .NET 10.0 and the existing codebase.

Changes

• Directory.Packages.props: Bumped 8 packages to latest compatible versions
• EssentialCSharp.Chat.Shared/Services/AIChatService.cs: Migrated to OpenAI SDK 2.10.0 API surface

Notable Dependency Updates

• Semantic Kernel: 1.72.0 → 1.76.0 (multiple features and fixes)
• ModelContextProtocol: 1.2.0 → 1.3.0
• Microsoft.Extensions.Http.Resilience: 10.5.0 → 10.6.0
• NuGet.Packaging/Protocol: 7.3.1 → 7.6.0
• Other: System.CommandLine, SourceLink, OpenTelemetry Profiler minor/patch versions

Breaking Changes & Mitigation

OpenAI SDK 2.10.0 (pulled via Semantic Kernel 1.76.0) deprecates the old Responses API. Migrated AIChatService from:

• OpenAIResponseClient → ResponsesClient
• ResponseCreationOptions → CreateResponseOptions

Updated method invocations to populate InputItems directly on options rather than as separate arguments. This maintains full feature parity while using the current SDK surface.

Verification

• Chat service tests pass (EssentialCSharp.Chat.Tests)
• Solution builds successfully
• No runtime or integration test failures observed

[Copilot]

Pull request overview

This PR upgrades several centrally-managed NuGet dependencies (notably Semantic Kernel / MCP-related packages) and updates AIChatService to the newer OpenAI Responses SDK API surface to keep the chat implementation compatible with the upgraded dependency graph.

Changes:

• Upgraded multiple NuGet package versions in Directory.Packages.props (Semantic Kernel, MCP, resilience, NuGet.* pins, etc.).
• Migrated AIChatService from the prior Responses client/options types to ResponsesClient + CreateResponseOptions.
• Updated streaming/non-streaming response creation to populate InputItems on options before calling the SDK.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
EssentialCSharp.Chat.Shared/Services/AIChatService.cs	Migrates chat response creation to the updated OpenAI Responses SDK types and request shape.
Directory.Packages.props	Updates centrally-managed package versions used across the solution.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (1)

EssentialCSharp.Chat.Shared/Services/AIChatService.cs:552

• CloneOptionsWithPreviousResponseId() doesn’t copy the configured model/deployment name. Since CreateResponseOptionsAsync sets options.Model = _Options.ChatDeploymentName, the cloned continuationOptions will have Model unset, which can cause tool-call continuation requests (and streaming continuations) to fail at runtime. Copy source.Model into the clone as well (and keep it consistent with the initial request).

        var clone = new CreateResponseOptions
        {
            Instructions = source.Instructions,
            PreviousResponseId = previousResponseId,
            EndUserId = source.EndUserId,
            ReasoningOptions = source.ReasoningOptions,
            MaxOutputTokenCount = source.MaxOutputTokenCount,