refactor(streaming): extract shared client-side stream into internal/…

[junliurs]

…clientstream

The client-side gRPC stream logic (send/recv event tracing, DoFinish idempotency, BizStatusError surfacing, recv-timeout handling and the client-streaming end-of-stream semantics) was duplicated between the network client (client package) and the in-process LocalCaller (server package).

Extract this shared behavior into a new internal/clientstream package exposing a reusable CommonStream, and add internal/localstream providing the in-process stream pair used by LocalCaller. Both client.stream and LocalCaller now embed CommonStream and inject transport-specific behavior (connection release, recv timeout, trace-finish ownership) through Options, so the two callers no longer maintain divergent copies.

internal/clientstream must not import client/server/remotecli to avoid import cycles.

No behavior change; existing client and server tests pass.

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[codecov]

Codecov Report

❌ Patch coverage is 76.04651% with 103 lines in your changes missing coverage. Please review.
✅ Project coverage is 62.97%. Comparing base (d27f7db) to head (40139f9).
⚠️ Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/localstream/localstream.go	66.66%	69 Missing and 2 partials ⚠️
server/local_caller.go	64.70%	11 Missing and 7 partials ⚠️
internal/clientstream/stream.go	91.80%	7 Missing and 3 partials ⚠️
internal/clientstream/grpc_stream.go	66.66%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1975      +/-   ##
==========================================
+ Coverage   62.84%   62.97%   +0.12%     
==========================================
  Files         394      398       +4     
  Lines       30267    30603     +336     
==========================================
+ Hits        19022    19272     +250     
- Misses       9948    10029      +81     
- Partials     1297     1302       +5     

Flag	Coverage Δ
integration	51.32% <29.53%> (-0.53%)	⬇️
unit	53.72% <70.46%> (+0.30%)	⬆️

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