Fix non-deterministic branch coverage in HedgingExecutionContext hedging delay tests

[Copilot]

The mutation tests for HedgingExecutionContext<T> were flaky because the condition at line 132 (if (!whenAnyHedgedTask.IsCompleted)) was not reliably exercised by both branches. The single existing test advanced the fake clock by a full day, firing both the hedging delay timer and the primary task timer simultaneously — making the outcome of the IsCompleted check dependent on non-deterministic async continuation scheduling.

Changes

• Replaced TryWaitForCompletedExecutionAsync_HedgedExecution_Ok with two deterministic, explicitly-asserted tests:
  • DelayFiresFirst_ReturnsNull — primary task delay (1 h) exceeds hedging delay (5 s); advancing only 10 s fires the hedging delay while the primary is still running, so whenAnyHedgedTask.IsCompleted is deterministically false and the method deterministically returns null (result.ShouldBeNull()).
  • TaskCompletesBeforeDelay_ReturnsTask — primary task delay (5 s) is less than hedging delay (1 h); advancing only 10 s completes the primary before the hedging delay timer fires, so whenAnyHedgedTask.IsCompleted is deterministically true and the method deterministically returns the completed execution (result.ShouldNotBeNull()).
• Both tests are parameterised with continueOnCapturedContext = true/false, preserving the original ConfigureAwait flag coverage.

With these changes, inverting the condition at line 132 will always cause at least one test to fail.

Confirm the following

• I started this PR by branching from the head of the default branch
• I have targeted the PR to merge into the default branch
• I have included unit tests for the issue/feature
• I have successfully run a local build

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.15%. Comparing base (fee0048) to head (04043fe).
⚠️ Report is 5 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2997   +/-   ##
=======================================
  Coverage   96.15%   96.15%           
=======================================
  Files         310      310           
  Lines        7135     7135           
  Branches     1005     1005           
=======================================
  Hits         6861     6861           
  Misses        221      221           
  Partials       53       53           

Flag	Coverage Δ
linux	96.15% <ø> (ø)
macos	96.15% <ø> (ø)
windows	96.15% <ø> (ø)

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[Copilot]

Pull request overview

This PR fixes flaky mutation/branch coverage around the whenAnyHedgedTask.IsCompleted check in HedgingExecutionContext<T>.TryWaitForCompletedExecutionAsync(...) by replacing a timing-racy hedging-delay test with two deterministic tests that explicitly drive each branch.

Changes:

• Replaced the previous single hedging-delay test with two deterministic tests that separately assert the “delay fires first” and “task completes first” outcomes.
• Preserved continueOnCapturedContext = true/false coverage for both new tests.
• Minor refactors/cleanup in the test file (consistent attribute ordering, reuse of common TimeSpan values, a few additional safety assertions).

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