add guard to avoid underflow and deleting needed nodesConfig

[BeniaminDrasovean]

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?

[Copilot]

Pull request overview

This PR prevents an unsigned integer underflow in removeOlderEpochs when epoch < maxDelta, which previously could cause unintended deletion of nodesConfig entries. It also adds focused unit tests to lock in the expected retention behavior for early epochs and normal pruning.

Changes:

• Added a guard in removeOlderEpochs to avoid epoch - maxDelta underflow and to prevent erroneous deletions.
• Refactored the deletion threshold into an epochToRemove variable for clarity.
• Added unit tests covering the “epoch < maxDelta” no-op case and the normal “remove only older epochs” case.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
sharding/nodesCoordinator/indexHashedNodesCoordinatorLite.go	Adds an early return to avoid underflow and uses a precomputed epochToRemove for correct pruning.
sharding/nodesCoordinator/indexHashedNodesCoordinatorLite_test.go	Adds tests validating no removals for early epochs and correct removal of only the oldest epoch once the delta threshold is reached.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.70%. Comparing base (a1cc8c6) to head (57bfb43).
⚠️ Report is 3 commits behind head on feat/testnet-fixes.

Additional details and impacted files

@@                 Coverage Diff                 @@
##           feat/testnet-fixes    #7908   +/-   ##
===================================================
  Coverage               77.69%   77.70%           
===================================================
  Files                     885      885           
  Lines                  126020   126023    +3     
===================================================
+ Hits                    97914    97921    +7     
+ Misses                  21626    21624    -2     
+ Partials                 6480     6478    -2     

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