fix: improve error handling in SDK message validation

[crStiv]

• Resolves TODO in handleSdkMessage function
• Adds detailed error context for message validation failures

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 46.12%. Comparing base (90b49fc) to head (dcacf15).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2135   +/-   ##
=======================================
  Coverage   46.12%   46.12%           
=======================================
  Files          78       78           
  Lines       10731    10731           
=======================================
  Hits         4950     4950           
  Misses       5339     5339           
  Partials      442      442           

Files with missing lines	Coverage Δ
x/wasm/keeper/handler_plugin.go	72.38% <100.00%> (ø)