feat(storage): support initial payload in bidi_write transport

[vsharonlynn]

Issue #5716 .

[gemini-code-assist]

Code Review

This pull request introduces the ability to send an initial chunk of data when opening an appendable object in a bidirectional write stream, updating the connector, state, and transport layers to support and test this flow. The review feedback points out that the newly added public methods connect_open_and_append and new_open_and_append lack documentation, violating the repository style guide which requires all public items to be documented with ///.

[codecov]

Codecov Report

❌ Patch coverage is 98.36830% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 96.36%. Comparing base (c4c8d56) to head (0237a51).
⚠️ Report is 48 commits behind head on main.

Files with missing lines	Patch %	Lines
src/storage/src/storage/bidi_write/connector.rs	97.28%	5 Missing ⚠️
src/storage/src/storage/bidi_write/state.rs	99.05%	1 Missing ⚠️
src/storage/src/storage/bidi_write/transport.rs	99.28%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6489      +/-   ##
==========================================
+ Coverage   96.34%   96.36%   +0.01%     
==========================================
  Files         295      295              
  Lines       83478    83850     +372     
==========================================
+ Hits        80429    80800     +371     
- Misses       3049     3050       +1     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[xlai20]

lgtm with an unresolved comment.