Handle transport start/stop failures

[BelfordZ]

Summary

• rollback already-started transports when a subsequent transport fails to start
• continue stopping remaining transports and surface aggregated errors
• add tests covering transport start rollback and stop failure scenarios

Testing

• npm test

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https://chatgpt.com/codex/tasks/task_e_68b362febd34832f8b83ca74050ec400

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.00%. Comparing base (eee4a4d) to head (320b68a).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #867      +/-   ##
==========================================
+ Coverage   98.96%   99.00%   +0.04%     
==========================================
  Files           9        9              
  Lines         289      302      +13     
  Branches       43       44       +1     
==========================================
+ Hits          286      299      +13     
  Misses          3        3              

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