feat(model_tokens): update default token budget and add new model

[ericmjl]

• Increase the default token budget from 2048 to 4096
• Add token budget for the new "mistral" model

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (4337998) 62.31% compared to head (7f13698) 62.31%.
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #20   +/-   ##
=======================================
  Coverage   62.31%   62.31%           
=======================================
  Files          47       47           
  Lines        1799     1799           
=======================================
  Hits         1121     1121           
  Misses        678      678           

Files	Coverage Δ
llamabot/bot/model_tokens.py	100.00% <100.00%> (ø)

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.