feat(core): validate outbound messages

[TimoGlastra]

Signed-off-by: Timo Glastra timo@animo.id

[codecov-commenter]

Codecov Report

Merging #526 (7fc61c4) into main (5e9a641) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #526      +/-   ##
==========================================
+ Coverage   86.27%   86.28%   +0.01%     
==========================================
  Files         266      266              
  Lines        5762     5767       +5     
  Branches      931      931              
==========================================
+ Hits         4971     4976       +5     
  Misses        790      790              
  Partials        1        1              

Impacted Files	Coverage Δ
packages/core/src/agent/MessageSender.ts	73.10% <100.00%> (+1.17%)	⬆️

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