Don't require gen_ai.system attribute on span events

[JamesNK]

Description

User reported issue that some GenAI messages weren't displayed in the visualizer. The problem is the dashboard incorrectly requires gen_ai.system attribute to be on span events, but the spec says they're only recommended: https://github.com/open-telemetry/semantic-conventions/blob/v1.36.0/docs/gen-ai/gen-ai-events.md#event-gen_aichoice

Semantic Kernel sometimes doesn't include the attribute. Its messages end up missing from the UI.

Checklist

• Is this feature complete?
  • Yes. Ready to ship.
  • No. Follow-up changes expected.
• Are you including unit tests for the changes and scenario tests if relevant?
  • Yes
  • No
• Did you add public API?
  • Yes
    • If yes, did you have an API Review for it?
      • Yes
      • No
    • Did you add <remarks /> and <code /> elements on your triple slash comments?
      • Yes
      • No
  • No
• Does the change make any security assumptions or guarantees?
  • Yes
    • If yes, have you done a threat model and had a security review?
      • Yes
      • No
  • No
• Does the change require an update in our Aspire docs?
  • Yes
    • Link to aspire-docs issue (consider using one of the following templates):
      • New (or update) doc-idea template
      • New breaking-change template
      • New diagnostic template
  • No

[github-actions]

🚀 Dogfood this PR with:

⚠️ WARNING: Do not do this without first carefully reviewing the code of this PR to satisfy yourself it is safe.

curl -fsSL https://raw.githubusercontent.com/dotnet/aspire/main/eng/scripts/get-aspire-cli-pr.sh | bash -s -- 11733

Or

• Run remotely in PowerShell:

iex "& { $(irm https://raw.githubusercontent.com/dotnet/aspire/main/eng/scripts/get-aspire-cli-pr.ps1) } 11733"

[Copilot]

Pull Request Overview

This PR fixes an issue where GenAI messages weren't displayed in the dashboard visualizer when the gen_ai.system attribute was missing from span events. The OpenTelemetry specification only recommends this attribute, but the dashboard was requiring it, causing Semantic Kernel messages to be excluded.

• Removes the requirement for gen_ai.system attribute on span events in the GenAI visualizer
• Updates the message detection logic to rely solely on event names for GenAI events
• Adds test coverage for GenAI events without the gen_ai.system attribute

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/Aspire.Dashboard/Model/GenAI/GenAIVisualizerDialogViewModel.cs	Updates message creation logic to detect GenAI events by name only, removing the system attribute requirement
tests/Aspire.Dashboard.Tests/Model/GenAIVisualizerDialogViewModelTests.cs	Adds test case for GenAI events without the gen_ai.system attribute

[JamesNK]

/backport to release/9.5

[github-actions]

Started backporting to release/9.5: https://github.com/dotnet/aspire/actions/runs/18121273259