Spork: add bounded retry policy for transient step-content download failures

[Copilot]

Step-content downloads in Spork currently fail fast on transient network conditions. This change adds bounded retries with jitter-free fixed backoff aligned to the requirement: up to 2 extra attempts after the first try, waiting 1s then 3s.

• Retry orchestration in download stage

  • StepsPlayer.DownloadContentAsync now routes content fetches through a retry wrapper.
  • Retry is applied only to transient failures; non-transient errors still fail immediately.
  • Maximum attempts are fixed at 3 total (initial + 2 retries) with delays [1s, 3s].

• Transient error classification

  • Added centralized transient detection in StepsPlayer:
    • HttpRequestException with 408, 429, or 5xx
    • TaskCanceledException, TimeoutException, IOException
    • Nested inner exceptions are recursively evaluated.

• Cancellation behavior

  • Cancellation-requested OperationCanceledException is propagated directly (no retry), including during retry-delay windows.

• Targeted unit coverage

  • Added focused tests for transient classification behavior (e.g., 503 => retryable, 404 => non-retryable).

private static readonly TimeSpan[] DownloadRetryDelays =
    [TimeSpan.FromSeconds(1d), TimeSpan.FromSeconds(3d)];

var hasMoreRetry = attempt < DownloadRetryDelays.Length;
if (!hasMoreRetry || !IsTransientDownloadException(ex))
    throw;

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✅ rkttu
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[Copilot]

Pull request overview

Adds a bounded retry policy to Spork step-content downloading so transient network/IO failures don’t fail fast, and introduces targeted unit tests to validate transient classification + retry-loop behavior.

Changes:

• Route StepsPlayer.DownloadContentAsync through a new retry wrapper with fixed backoff delays (1s, then 3s; max 3 total attempts).
• Add centralized transient-failure detection (IsTransientDownloadException + status code classification).
• Add unit tests covering retryable/non-retryable status codes, socket/IO-level failures, and retry-loop attempt counts.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/Spork.App/Steps/Implementations/StepsPlayer.cs	Implements retry loop + transient exception/status-code classification for step content downloads.
src/Spork.Test/StepsPlayerRetryLoopTests.cs	Verifies retry loop attempt limits and stop-on-success behavior.
src/Spork.Test/StepsPlayerStatusCodeClassificationTests.cs	Tests HTTP status code-based transient classification.
src/Spork.Test/StepsPlayerSocketFailureTests.cs	Tests socket/IO failure classification including inner-exception recursion.
src/Spork.Test/StepsPlayerTransientDownloadTests.cs	Adds basic transient classification tests for a few representative exception types.

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