[WIP] Resolve merge conflicts in pull request #10663

[Copilot]

• Fetch the PR [http-client-csharp] Adopt Spector multiple-services scenario tests #10663 branch and the latest main, then reproduce the merge locally
• Inspect each merge conflict and preserve both the PR's multiple-services Spector adoption changes and main updates
• Run focused http-client-csharp build/generation/tests to validate the resolved merge
• Run final validation and push the resolved merge back to the PR branch

Original prompt

Resolve the merge conflicts in pull request #10663 (#10663).

Steps:

1. Check out the PR branch for [http-client-csharp] Adopt Spector multiple-services scenario tests #10663.
2. Merge the latest base branch (main) into the PR branch.
3. Resolve all merge conflicts carefully, preserving the intent of both sides:
   • The PR adds adoption of Spector multiple-services scenario tests for http-client-csharp.
   • Make sure the changes from the PR (test scaffolding, generated code, configuration for multiple-services scenarios) are preserved alongside any updates from main.
4. Ensure the project still builds and tests pass for the affected http-client-csharp generator.
5. Push the conflict resolution back to the PR branch.

Do not change behavior beyond what is required to resolve the conflicts.

The following is the prior conversation context from the user's chat exploration (may be truncated):

User: resolve the merge conflicts in this pull request

Assistant: I've asked the coding agent to resolve the merge conflicts in PR #10663 — waiting for your confirmation on the dialog to proceed.

This pull request was created from Copilot chat.