[ISSUE #10870] fix(client): preserve maximum process queue offset

[yuluo-yx]

Which Issue(s) This PR Fixes

• Fixes [Bug] ProcessQueue may return a stale next offset for out-of-order messages #10870

Brief Description

ProcessQueue previously overwrote queueOffsetMax with the last newly inserted message. This change retains the numeric maximum so an out-of-order batch cannot make removeMessage return a stale next offset.

How Did You Test This Change?

• mise exec java@zulu-8.94.0.17 -- mvn -pl client -am -DskipITs -Dtest=ProcessQueueTest -Dsurefire.failIfNoSpecifiedTests=false test (9 tests passed)
• Checkstyle and SpotBugs passed in the same Maven reactor.
• git diff --check and the 400-line scope gate passed.
• Not run: full repository build, container tests, or end-to-end tests.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 48.28%. Comparing base (fd0c959) to head (4d280e2).

Additional details and impacted files

@@              Coverage Diff              @@
##             develop   #10880      +/-   ##
=============================================
- Coverage      48.39%   48.28%   -0.12%     
+ Complexity     13562    13523      -39     
=============================================
  Files           1380     1380              
  Lines         101165   101165              
  Branches       13127    13127              
=============================================
- Hits           48962    48849     -113     
- Misses         46233    46320      +87     
- Partials        5970     5996      +26     

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[RockteMQ-AI]

LGTM. Trivial change, looks good.

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