fix: handle invalid websocket JSON

[belfzclaw]

Summary\n- catch JSON.parse failures in the ws transport and reply with a JSON-RPC -32700 error\n- add regression test to ensure a bad frame doesn't crash the server\n\nFixes #748

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.97%. Comparing base (8531407) to head (91e776e).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #874      +/-   ##
==========================================
+ Coverage   98.96%   98.97%   +0.01%     
==========================================
  Files           9        9              
  Lines         289      292       +3     
  Branches       43       44       +1     
==========================================
+ Hits          286      289       +3     
  Misses          3        3              

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