mux stream kind mismatch fix (CON-240)

[pompon0]

Made mux stream opening more strict:

• explicit kind when OPEN frame
• kind mismatch is detected instead of ignored
  Added relevant tests.

[github-actions]

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Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Apr 10, 2026, 10:00 AM

[codecov]

Codecov Report

❌ Patch coverage is 72.72727% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.79%. Comparing base (8d751f6) to head (34ee54a).
⚠️ Report is 15 commits behind head on main.

Files with missing lines	Patch %	Lines
sei-tendermint/internal/p2p/mux/mux.go	77.77%	1 Missing and 1 partial ⚠️
sei-tendermint/internal/p2p/mux/stream_state.go	50.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3209   +/-   ##
=======================================
  Coverage   58.79%   58.79%           
=======================================
  Files        2054     2054           
  Lines      168303   168305    +2     
=======================================
+ Hits        98948    98952    +4     
+ Misses      60609    60608    -1     
+ Partials     8746     8745    -1     

Flag	Coverage Δ
sei-chain-pr	79.60% <72.72%> (?)
sei-db	70.41% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
sei-tendermint/internal/p2p/mux/stream_state.go	91.66% <50.00%> (+4.16%)	⬆️
sei-tendermint/internal/p2p/mux/mux.go	77.77% <77.77%> (+0.19%)	⬆️

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