feat(partitions): add poll_messages support to simulator

[krishvishal]

Summary

• Implement poll_messages, store_consumer_offset, get_consumer_offset, and offsets on IggyPartition, wired through Simulator.
• Fix send_messages client wire format to emit 64-byte IggyMessage headers and 16-byte indexes.
• Fix StoreConsumerOffset replication: add consumer_kind byte so consumer group offsets route to the correct map.
• Enforce committed-offset guard on PollingKind::Timestamp polling

Closes #2961

[codecov]

Codecov Report

❌ Patch coverage is 0% with 231 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.80%. Comparing base (9c8b5cc) to head (cba7cf2).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
core/partitions/src/iggy_partition.rs	0.00%	114 Missing ⚠️
core/simulator/src/main.rs	0.00%	42 Missing ⚠️
core/simulator/src/client.rs	0.00%	33 Missing ⚠️
core/simulator/src/lib.rs	0.00%	27 Missing ⚠️
core/partitions/src/iggy_partitions.rs	0.00%	15 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #2960      +/-   ##
============================================
- Coverage     71.98%   71.80%   -0.19%     
  Complexity      925      925              
============================================
  Files          1113     1113              
  Lines         92345    92569     +224     
  Branches      69896    70128     +232     
============================================
- Hits          66471    66465       -6     
- Misses        23315    23533     +218     
- Partials       2559     2571      +12     

Flag	Coverage Δ
csharp	67.43% <ø> (-0.21%)	⬇️
go	36.38% <ø> (ø)
java	61.91% <ø> (ø)
node	91.28% <ø> (-0.26%)	⬇️
python	81.43% <ø> (ø)
rust	72.52% <0.00%> (-0.22%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
core/partitions/src/iggy_partitions.rs	0.00% <0.00%> (ø)
core/simulator/src/lib.rs	0.00% <0.00%> (ø)
core/simulator/src/client.rs	0.00% <0.00%> (ø)
core/simulator/src/main.rs	0.00% <0.00%> (ø)
core/partitions/src/iggy_partition.rs	0.00% <0.00%> (ø)

... and 11 files with indirect coverage changes

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[krishvishal]

FAIL [   0.555s] (1041/1649) integration::mod cli::personal_access_token::test_pat_login_options::should_be_successful
FAIL [   0.224s] (1051/1649) integration::mod cli::system::test_cli_session_scenario::should_be_successful

Looks like flaky tests.

[hubcio]

@krishvishal i will check that.

[hubcio]

This should fix the problem with flaky test, I think... #2963