Fix PicklingError for discovered agent modules in dev mode

[mahimairaja]

Problem

Running python main.py dev in the examples directory fails with:

_pickle.PicklingError: Can't pickle <class 'openrtc_discovered_dental.DentalAgent'>: import of module 'openrtc_discovered_dental' failed

This occurs because _load_agent_module dynamically loads agent modules using importlib.util but never registers them in sys.modules. When LiveKit's dev mode uses watchfiles.arun_process() → multiprocessing, it needs to pickle DentalAgent. Pickling a class requires its module to be importable by name, which fails without an entry in sys.modules.

Fix

Register dynamically loaded agent modules in sys.modules before execution, following the standard importlib pattern:

1. Add the module to sys.modules before calling exec_module() (supports self-references during execution)
2. Clean up sys.modules on failure to avoid leaving partial state

Testing

All 36 existing tests pass.

  

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.05%. Comparing base (f46e619) to head (4fa2f8f).
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Additional details and impacted files

@@                  Coverage Diff                   @@
##           fix/pickling-issue      #13      +/-   ##
======================================================
+ Coverage               87.92%   88.05%   +0.13%     
======================================================
  Files                       3        3              
  Lines                     265      268       +3     
======================================================
+ Hits                      233      236       +3     
  Misses                     32       32              

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