Consensus subround dowork improvement

[ssd04]

Reasoning behind the pull request

Proposed changes

Testing procedure

Pre-requisites

Based on the Contributing Guidelines the PR author and the reviewers must check the following requirements are met:

• was the PR targeted to the correct branch?
• if this is a larger feature that probably needs more than one PR, is there a feat branch created?
• if this is a feat branch merging, do all satellite projects have a proper tag inside go.mod?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.47%. Comparing base (af9046b) to head (c07b03f).

Additional details and impacted files

@@                  Coverage Diff                   @@
##           feat/testnet-fixes    #7918      +/-   ##
======================================================
+ Coverage               77.45%   77.47%   +0.01%     
======================================================
  Files                     887      887              
  Lines                  126472   126476       +4     
======================================================
+ Hits                    97964    97985      +21     
+ Misses                  22057    22042      -15     
+ Partials                 6451     6449       -2     

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[Copilot]

Pull request overview

This PR improves SPoS consensus subround execution by making DoWork responsive to context cancellation, adds a regression test for this behavior, and introduces a safer test-only accessor for received messages while also doing a small cleanup in message validation.

Changes:

• Add ctx.Done() handling in Subround.DoWork() to abort work and mark the round as canceled.
• Add a unit test ensuring DoWork returns false and sets the canceled flag when the context is closed.
• In test helpers, return a cloned copy of Worker.receivedMessages, and simplify header access in consensusMessageValidator.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
consensus/spos/subround.go	Adds context-cancellation handling to stop subround work early.
consensus/spos/subround_test.go	Adds coverage for the new context-cancellation behavior in DoWork.
consensus/spos/export_test.go	Adjusts test-only ReceivedMessages() accessor to avoid returning the internal map directly.
consensus/spos/consensusMessageValidator.go	Minor refactor: cache header lookup and remove an obsolete comment.

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