docs: Document Fn Execution API protos

[damccorm]

Description

Add documentation comments to previously undocumented messages, fields, and enums in the Beam Fn API protos, which define the gRPC interface between the SDK harness and runner harness.

Files Changed

File	Changes
beam_fn_api.proto	ProcessBundleResponse, ProcessBundleProgressResponse, FinalizeBundleRequest/Response, Elements.DrainMode, StateRequest/Response, BeamFnState service, StateKey, OrderedListRange, LogControl, StartWorkerRequest/Response, StopWorkerRequest/Response, BeamFnExternalWorkerPool service
beam_provision_api.proto	Consistency fix on dependencies field

Notes

• All changes are comment-only — no code, field numbers, types, or options modified
• This is part of a 3-PR set documenting all model protos

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 58.70%. Comparing base (1ca1faf) to head (1c7efa5).
⚠️ Report is 521 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #39293      +/-   ##
============================================
- Coverage     58.73%   58.70%   -0.03%     
  Complexity     7418     7418              
============================================
  Files          1649     1649              
  Lines        212369   212787     +418     
  Branches       6330     6330              
============================================
+ Hits         124727   124926     +199     
- Misses        83095    83314     +219     
  Partials       4547     4547              

Flag	Coverage Δ
python	79.71% <ø> (-0.18%)	⬇️

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[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request focuses on enhancing the maintainability and understandability of the Beam Fn API by adding descriptive documentation comments to the existing protobuf definitions. These changes are strictly limited to documentation and do not alter the underlying code, field numbers, or data structures, ensuring full backward compatibility.

Highlights

• Documentation Updates: Added comprehensive documentation comments to various messages, fields, and enums within the Beam Fn API protos to improve clarity for the gRPC interface.
• Consistency Improvements: Standardized documentation style and fixed a minor consistency issue regarding the 'dependencies' field in the Provision API.

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[gemini-code-assist]

Code Review

This pull request adds comprehensive documentation and comments to various Protobuf messages, fields, and services within the Beam Fn API (beam_fn_api.proto) and the Provision API (beam_provision_api.proto). These additions clarify the roles of requests, responses, and services like worker management, state APIs, and bundle processing. There are no review comments, so I have no feedback to provide.

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