feat(nvim): tuned system prompt and added project_root to the tool output.

[Davidyz]

This PR tuned the system prompt so that the model shouldn't include the <path> </path> tags in the answer.

This also added the project_root to the tool output presented to the user, so that users have a better idea about whether the tool call was appropriate when performing joint search.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.24%. Comparing base (9744867) to head (22366fb).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #129   +/-   ##
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  Coverage   99.24%   99.24%           
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  Files          22       22           
  Lines        1463     1463           
=======================================
  Hits         1452     1452           
  Misses         11       11           

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