feat(server): return base_offset and partition_id from send_messages

[sujitn]

The offset assigned during append was computed but discarded. Propagate it through ShardResponse::SendMessages and include it in the binary protocol response.

Wire format change:
Before: [status:4 LE][length:4 LE (0)]
After: [status:4 LE][length:4 LE (12)][base_offset:8 LE][partition_id:4 LE]

existing SDK clients (excluding node) read the length field and skip unknown body bytes. The send_messages wrapper discards the response body and returns Ok(()).

Fixed node SDK to ignore length

Ref: #3044

Local Execution

• Passed
• Pre-commit hooks ran

AI Usage

If AI tools were used, please answer:

1. Which tools?
   Claude

2. Scope of usage?
   SDK validation

3. How did you verify the generated code works correctly?

• 64/64 server unit tests pass (cargo test -p server --lib)
• 36/36 offset retrieval integration tests pass, these send messages via the SDK
• 87/87 concurrent produce/consume integration tests pass
• 6/6 authentication integration tests pass
• cargo clippy -p server --all-targets -- -D warnings - 0 warnings

4. Can you explain every line of the code if asked?
   Yes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.73%. Comparing base (aa34566) to head (c130f35).
⚠️ Report is 23 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #3101      +/-   ##
============================================
- Coverage     72.75%   72.73%   -0.02%     
  Complexity      943      943              
============================================
  Files          1117     1117              
  Lines         96343    96335       -8     
  Branches      73544    73552       +8     
============================================
- Hits          70092    70067      -25     
- Misses        23700    23703       +3     
- Partials       2551     2565      +14     

Components	Coverage Δ
Rust Core	73.50% <ø> (-0.01%)	⬇️
Java SDK	62.30% <ø> (ø)
C# SDK	69.10% <ø> (-0.31%)	⬇️
Python SDK	81.43% <ø> (ø)
Node SDK	91.53% <100.00%> (ø)
Go SDK	38.97% <ø> (ø)

Files with missing lines	Coverage Δ
.../binary/handlers/messages/send_messages_handler.rs	100.00% <ø> (ø)
core/server/src/http/http_shard_wrapper.rs	74.12% <ø> (-0.18%)	⬇️
core/server/src/shard/handlers.rs	77.83% <ø> (-0.12%)	⬇️
core/server/src/shard/system/messages.rs	87.84% <ø> (+0.08%)	⬆️
core/server/src/shard/transmission/frame.rs	100.00% <ø> (ø)
foreign/node/src/client/client.utils.ts	89.89% <100.00%> (ø)

... and 16 files with indirect coverage changes

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[hubcio]

I'm gonna review this properly once we finalize current release 0.8.0.

[lukaszzborek]

I think we should at least create issues for every sdk to implement that change in api (just after merge)

[github-actions]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs.

If you need a review, please ensure CI is green and the PR is rebased on the latest master. Don't hesitate to ping the maintainers - either @core on Discord or by mentioning them directly here on the PR.

Thank you for your contribution!

[hubcio]

We decided to postpone this until cluster v0 is merged.
I'll resume discussion at some point in future one of these threads:
#3081
#6

Until then, no code should be written besides spikes/PoCs. Of course, design studies can be continued.