Make abort E2E snapshots tolerate timing variants

[stephentoub]

Abort E2E tests can produce different valid request histories depending on when AbortAsync lands. Runtime PR investigations saw C# replay mismatches where an in-flight tool result was interrupted instead of recorded as a missing tool, and where streaming abort retained the original user prompt while dropping the aborted assistant response.

This updates the affected replay snapshots with those legal alternatives. No production code changes are included: the tests still cover the public contract that abort completes and the session remains usable, while the cassettes stop requiring a single timing-dependent history.

Validation:

• GITHUB_ACTIONS=true dotnet test dotnet\test\GitHub.Copilot.SDK.Test.csproj --filter "FullyQualifiedName=GitHub.Copilot.Test.E2E.SessionE2ETests.Should_Abort_A_Session|FullyQualifiedName~GitHub.Copilot.Test.E2E.AbortE2ETests"
• Synthetic replay requests for the two reported CI histories matched the updated snapshots
• git diff --check

[Copilot]

Pull request overview

Updates the replay-proxy YAML cassettes used by the .NET E2E abort tests to accept multiple valid request histories that differ based on when AbortAsync takes effect. This keeps the tests focused on the public contract (abort completes and the session remains usable) while removing timing-dependent brittleness in the recorded histories.

Changes:

• Add an alternative should_abort_a_session conversation where both tool calls are recorded as interrupted (instead of “missing tool” + interrupted).
• Add an alternative should_abort_during_active_streaming conversation where the original long user prompt is retained but the aborted assistant response is dropped before the recovery prompt.

Show a summary per file

File	Description
test/snapshots/session/should_abort_a_session.yaml	Adds an additional valid abort-timing variant where both tool calls are interrupted.
test/snapshots/abort/should_abort_during_active_streaming.yaml	Adds a streaming-abort variant where the initial user prompt remains in history but the aborted assistant message is absent.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 0
• Review effort level: Low