feat(agent): log agent version on startup

[Utkarsh9571]

Logs the agent version at startup using zerolog for better traceability and debugging.

Only modifies cmd/agent/core/agent.go as requested. No changes to other files.

Let me know if you'd like to adjust the log level, format, or placement.

[qwerty287]

Thanks, that's what I mean.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 21.47%. Comparing base (1432037) to head (747bb77).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5724      +/-   ##
==========================================
- Coverage   21.48%   21.47%   -0.02%     
==========================================
  Files         428      428              
  Lines       38550    38550              
==========================================
- Hits         8283     8278       -5     
- Misses      29503    29508       +5     
  Partials      764      764              

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[Utkarsh9571]

thank you