Weaviate Agents extras integration

[cdpierse]

• Adds weaviate_agents package as an optional extra.
• Add type stub files (.pyi) for the agents module to provide proper type hints for the optional weaviate-agents functionality. These stubs maintain type information while gracefully handling cases where the weaviate-agents package is not installed.

[orca-security-eu]

Orca Security Scan Summary

Status	Check	Issues by priority
Passed	Infrastructure as Code	0   0   0   0	View in Orca
Passed	SAST	0   0   0   0	View in Orca
Passed	Secrets	0   0   0   0	View in Orca
Passed	Vulnerabilities	0   0   0   0	View in Orca

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 88.36%. Comparing base (efd9955) to head (b1455d4).
Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
weaviate/exceptions.py	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1562      +/-   ##
==========================================
+ Coverage   88.25%   88.36%   +0.10%     
==========================================
  Files         186      186              
  Lines       15875    15882       +7     
==========================================
+ Hits        14011    14034      +23     
+ Misses       1864     1848      -16     

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[dirkkul]

do we need these .pyi files in addition to the .py file?

[cdpierse]

Yes the .pyi stubs give us the ability to provide type hints for the optional package functionality when required by giving the type checkers the right hints but because they are not real __init__.py files the none of the paths will work at runtime if extras is not installed.