[ISSUE 9535]: Prevent first message loss in CONSUME_FROM_LAST_OFFSET #7187

[mengnankkkk]

…empty/single-message queues #9535

Which Issue(s) This PR Fixes

When maxOffset <= 1, start from offset 0 to ensure no messages are skipped
maxOffset = 0: empty queue, start from 0 (no messages to consume)
maxOffset = 1: single message at offset 0, start from 0 to consume it
maxOffset > 1: multiple messages, start from maxOffset (last position)

Fixes #9535

Brief Description

How Did You Test This Change?

Added 8 new test methods to the existing RebalancePushImplTest class to test various edge cases of the maxOffset method.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 48.00%. Comparing base (40e3aa9) to head (8f48022).
Report is 1 commits behind head on develop.

Files with missing lines	Patch %	Lines
...cketmq/client/impl/consumer/RebalancePushImpl.java	80.00%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop    #9552      +/-   ##
=============================================
- Coverage      48.12%   48.00%   -0.13%     
+ Complexity     12067    12040      -27     
=============================================
  Files           1313     1313              
  Lines          92767    92770       +3     
  Branches       11862    11863       +1     
=============================================
- Hits           44647    44530     -117     
- Misses         42625    42728     +103     
- Partials        5495     5512      +17     

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