CancellationToken ignored or misused in several async methods

[rido-min]

Summary

Several async methods accept a CancellationToken parameter but either ignore it, pass CancellationToken.None instead, or use the wrong token. This means callers cannot cancel operations even when they provide a token.

Locations

Passes CancellationToken.None instead of the provided parameter

• Teams.AI.Models.OpenAI/OpenAIChatModel.Send.cs:51 — ChatClient.CompleteChatAsync(chatMessages, requestOptions, CancellationToken.None) ignores the cancellationToken parameter received at line 27
• Teams.AI.Models.OpenAI/OpenAIChatModel.Send.cs:92 — ChatClient.CompleteChatStreamingAsync(chatMessages, requestOptions, CancellationToken.None) ignores the cancellationToken parameter received at line 71

Uses wrong token (context property instead of parameter)

• Teams.Apps/Contexts/Context.Send.cs:64 — await Sender.Send(activity, Ref, CancellationToken) uses the context's CancellationToken property instead of the cancellationToken method parameter

Token not propagated to underlying call

• Teams.Common/Http/HttpClient.cs:60 — await _client.SendAsync(httpRequest) does not pass the available cancellationToken to the underlying HttpClient.SendAsync

Token accepted but unused

• Teams.Common/Http/HttpClient.cs:121, 146 — CreateResponse methods accept CancellationToken but never use it

Missing from interface method

• Teams.AI/ChatPlugin.cs:69 — OnBuildInstructions is the only method in the interface missing a CancellationToken parameter (all other methods have one)
• Teams.AI/BaseChatPlugin.cs:39 — Corresponding base implementation also missing the parameter

Impact

• OpenAI API calls are effectively uncancellable — request timeouts and graceful shutdown cannot abort in-flight calls
• The Context.Send bug means per-call cancellation tokens passed by callers are silently ignored
• HTTP calls in Teams.Common cannot be cancelled at the transport level

Suggested fix

• Replace CancellationToken.None with the cancellationToken parameter
• Fix the parameter shadowing in Context.Send.cs
• Propagate the token through HttpClient.SendAsync and CreateResponse
• Add CancellationToken to OnBuildInstructions interface method