Fix C# plugin E2E tests for live local marketplaces

[stephentoub]

Summary

• make the C# plugin RPC E2E fixture distinguish copied installs from live local-marketplace plugins through observable behavior
• move the fixture version into the plugin manifest, then edit it in place from v1 to v2 after installation
• preserve strict assertions for both modes:
  • copied installs retain v1 until update, install skills, and produce update/update-all entries
  • live plugins immediately expose v2, install without copying skills, no-op single updates, and are omitted from raw update-all results
• keep install/list and enable/disable coverage authoritative by checking the post-mutation plugin listing

This restores compatibility with both the CLI version pinned by copilot-sdk and current github/copilot-agent-runtime main after live repo-local marketplace loading was introduced.

Validation

• dotnet format dotnet\test\GitHub.Copilot.SDK.Test.csproj --verify-no-changes --no-restore --include dotnet\test\E2E\RpcServerPluginsE2ETests.cs
• affected E2E class against the SDK-pinned @github/copilot 1.0.81-6 CLI: 7 passed
• affected E2E class against copilot-agent-runtime main at fdac918608 using its Windows test-build-Windows artifact: 7 passed

[Copilot]

Pull request overview

Updates C# plugin RPC E2E tests to support both copied and live local-marketplace plugin behavior.

Changes:

• Moves fixture versioning into plugin.json.
• Adds strict assertions for install, update, and update-all semantics in both modes.
• Verifies post-mutation plugin listings.

Show a summary per file

File	Description
dotnet/test/E2E/RpcServerPluginsE2ETests.cs	Adapts local-marketplace E2E fixtures and assertions for copied and live plugins.

Review details

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• Files reviewed: 1/1 changed files
• Comments generated: 0
• Review effort level: Balanced

[github-actions]

Cross-SDK Consistency Review ✅

This PR modifies only dotnet/test/E2E/RpcServerPluginsE2ETests.cs — a single .NET E2E test file with no production SDK code changes and no public API surface modifications.

No cross-SDK consistency issues identified. The changes are purely test fixture improvements to handle two plugin installation modes (copied vs. live local-marketplace). This doesn't introduce any new public API or behavioral change that would need to be mirrored in Node.js, Python, Go, Java, or Rust SDKs.

Generated by SDK Consistency Review Agent for #2373 · sonnet46 16.5 AIC · ⌖ 4 AIC · ⊞ 6.6K · ◷