ai/live: Set the default model on the request if needed

[j0sh]

Without it, the O does not have a model ID to initialize the job

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 34.03496%. Comparing base (abd997d) to head (6f07a1d).
Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
server/ai_process.go	0.00000%	3 Missing ⚠️

Additional details and impacted files

@@                 Coverage Diff                 @@
##              master       #3313         +/-   ##
===================================================
- Coverage   34.03772%   34.03496%   -0.00276%     
===================================================
  Files            141         141                 
  Lines          37006       37009          +3     
===================================================
  Hits           12596       12596                 
- Misses         23691       23694          +3     
  Partials         719         719                 

Files with missing lines	Coverage Δ
server/ai_process.go	0.60606% <0.00000%> (-0.00158%)	⬇️

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Files with missing lines	Coverage Δ
server/ai_process.go	0.60606% <0.00000%> (-0.00158%)	⬇️