Stabilize C# rewind E2E initialization

[stephentoub]

The C# rewind E2E can send its first file-mutating turn before runtime file-change tracking has established the initial baseline. When that race occurs, the first capture is incomplete and the test times out waiting for two restorable rewind points.

Wait for session.history.listRewindPoints to report enabled tracking with an initialized empty point set before sending the first edit. This matches the runtime protocol E2E synchronization and preserves the existing behavior under test.

Validation: the focused rewind E2E passed 10 consecutive runs against Copilot CLI 1.0.84-6, and the rewind plus MCP OAuth lifecycle tests passed together.

Generated by Copilot

[Copilot]

Copilot review overview

🟢 Approval recommended

The focused synchronization correctly addresses the initialization race without altering tested behavior.

Review tier: Balanced
Findings: None

What changed in this PR

Adds synchronization to prevent the C# rewind E2E from mutating files before tracking initialization completes.

Changes:

• Polls until file-change tracking is enabled with no rewind points.
• Provides a 30-second timeout with a clear failure message.

File	Description
dotnet/​test/​E2E/​RewindE2ETests.cs	Waits for tracking initialization before the first edit.

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[github-actions]

SDK Consistency Review — PR #2661

Scope of change: Only dotnet/test/E2E/RewindE2ETests.cs was modified (12 additions), adding a TestHelper.WaitForConditionAsync poll that waits for rewind-point tracking to initialize (UnavailableReason is null, FileChangeTrackingEnabled, and an empty initial Points list) before proceeding with the existing test flow.

Finding: No consistency issue. This change is confined to a .NET E2E test file and does not touch any SDK client/library code (dotnet/src/, nodejs/src/, python/copilot/, go/, java/sdk/src/main/java/, rust/src/) or public API surface. It's a test-reliability fix (avoiding a race condition where rewind points might not yet be tracked when the test proceeds), not a new feature or behavior change in the SDK itself, so there is nothing to mirror in the other language SDKs.

No action needed for cross-SDK parity.

Generated by SDK Consistency Review Agent for #2661 · copilot · sonnet50 · 18.1 AIC · ⌖ 12.1 AIC · ⊞ 8.3K · ◷