fix(python): read consumer metadata without the consumer lock

[ethanlin01x]

Which issue does this PR address?

Relates to #3776 (Found while reviewing)

Rationale

The synchronous getters on the Python IggyConsumer took the consumer mutex with blocking_lock() while holding the GIL, and consume_messages holds that mutex for the whole consumption run. Reading an attribute during consumption hung the interpreter; reading one from a callback panicked inside the Tokio runtime. Neither is recoverable from Python.

consume = consumer.consume_messages(handle, shutdown_event)
print(consumer.name())   # never returns

What changed?

None of those getters need exclusive access.

name, stream and topic never change after construction, so the Python wrapper snapshots them. The partition id and offsets do change, but already live behind Arcs in the Rust SDK, which now hands them out as IggyConsumerState via IggyConsumer::state(). The wrapper keeps a clone and reads them as atomic loads, never taking the lock.

Additive on the Rust side. On the Python side stream() and topic() now return the identifier directly instead of a PyResult.

Local Execution

• Passed
• Pre-commit hooks ran

AI Usage

1. Which tools? Claude
2. Scope of usage? help implement and write PR description
3. How did you verify the generated code works correctly? Ran the Python test suite against a real server
4. Can you explain every line of the code if asked? Yes, all the changes are checked by the human.

[codecov]

Codecov Report

❌ Patch coverage is 67.74194% with 20 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.79%. Comparing base (c0c7493) to head (004e7cb).

Files with missing lines	Patch %	Lines
core/sdk/src/clients/consumer.rs	56.52%	20 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #3888      +/-   ##
============================================
- Coverage     83.84%   83.79%   -0.05%     
  Complexity     1358     1358              
============================================
  Files          1212     1212              
  Lines        166843   166869      +26     
  Branches     134306   134454     +148     
============================================
- Hits         139890   139830      -60     
+ Misses        23312    23256      -56     
- Partials       3641     3783     +142     

Components	Coverage Δ
Rust Core	84.65% <56.52%> (+0.03%)	⬆️
Java SDK	66.67% <ø> (ø)
C# SDK	74.99% <ø> (-1.56%)	⬇️
Python SDK	90.14% <100.00%> (+<0.01%)	⬆️
PHP SDK	84.48% <ø> (ø)
Node SDK	95.84% <ø> (ø)
Go SDK	68.32% <ø> (ø)

Files with missing lines	Coverage Δ
foreign/python/src/client.rs	99.85% <100.00%> (+<0.01%)	⬆️
foreign/python/src/consumer.rs	81.81% <100.00%> (-0.43%)	⬇️
core/sdk/src/clients/consumer.rs	71.05% <56.52%> (-0.72%)	⬇️

... and 74 files with indirect coverage changes

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[ethanlin01x]

/request-review @hubcio

[ethanlin01x]

/ready