fix(schema): agentic concat support extra

[meguminnnnnnnnn]

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[codecov]

Codecov Report

❌ Patch coverage is 45.45455% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.79%. Comparing base (427e960) to head (436dceb).
⚠️ Report is 1 commits behind head on release/agentic_model.

Files with missing lines	Patch %	Lines
schema/agentic_message.go	45.45%	4 Missing and 2 partials ⚠️

Additional details and impacted files

@@                    Coverage Diff                    @@
##           release/agentic_model     #670      +/-   ##
=========================================================
- Coverage                  78.86%   78.79%   -0.08%     
=========================================================
  Files                        132      132              
  Lines                      13231    13241      +10     
=========================================================
- Hits                       10435    10433       -2     
- Misses                      1928     1938      +10     
- Partials                     868      870       +2     

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