feat: support websocket first message method response code

[withchao]

🔍 What type of PR is this?

👀 What this PR does / why we need it:

• My pull request adheres to the code style of this project
• My code requires changes to the documentation
• I have updated the documentation as required
• All the tests have passed

🅰 Which issue(s) this PR fixes:

Fixes #1650

📝 Special notes for your reviewer:

🎯 Describe how to verify it

📑 Additional documentation e.g., RFC, notion, Google docs, usage docs, etc.:

[sweep-ai]

Apply Sweep Rules to your PR?

• Apply: All new business logic should have corresponding unit tests.
• Apply: Refactor large functions to be more modular.
• Apply: Add docstrings to all functions and file headers.

[codecov]

Codecov Report

Attention: 64 lines in your changes are missing coverage. Please review.

Comparison is base (49f4e3f) 5.12% compared to head (2d295e2) 5.11%.

Files	Patch %	Lines
internal/msggateway/n_ws_server.go	0.00%	64 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##            main   #1651      +/-   ##
========================================
- Coverage   5.12%   5.11%   -0.02%     
========================================
  Files         42      42              
  Lines       3782    3792      +10     
========================================
  Hits         194     194              
- Misses      3577    3587      +10     
  Partials      11      11              

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