fix(storage): use server-reported size on stream reconnect to avoid duplicate writes

[v-pratap]

Problem: When the C++ SDK loses connection while writing to an appendable (Rapid) object and tries to reconnect, it sometimes sends data that the server has already received. This happens because the client was ignoring the current object size reported by the server during the reconnect, and instead relied on its own older progress information saved before the connection dropped. This caused the server to reject the writes as out-of-range.

Solution: Modified the client to check the server's response immediately after reconnecting. If the server returns the current size of the object (and a handle to continue writing), the client now uses that size as the starting offset for sending new data. This prevents the client from re-sending data that the server already has.

[gemini-code-assist]

Code Review

This pull request updates the AsyncWriterConnectionResumedState class to extract the persisted offset directly from the first response's resource size or persisted size when resuming a write operation, falling back to the persisted state if neither is present. A corresponding unit test has also been added to verify this behavior. The review feedback suggests optimizing performance by using std::move to avoid copying the protobuf resource message when finalizing the object.

[codecov]

Codecov Report

❌ Patch coverage is 92.55319% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.71%. Comparing base (77109ef) to head (ddfdfd6).

Files with missing lines	Patch %	Lines
...torage/internal/async/writer_connection_resumed.cc	50.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16115      +/-   ##
==========================================
- Coverage   92.71%   92.71%   -0.01%     
==========================================
  Files        2353     2353              
  Lines      219274   219364      +90     
==========================================
+ Hits       203303   203386      +83     
- Misses      15971    15978       +7     

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