fix: forbid global project in conda base env

[frostming]

Signed-off-by: Frost Ming [email protected]

Close #2409

Pull Request Checklist

• A news fragment is added in news/ describing what is new.
• Test cases added for changed code.

Describe what you have changed in this PR.

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (73651b7) 84.51% compared to head (406727b) 84.52%.

Files	Patch %	Lines
src/pdm/project/core.py	87.50%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2410   +/-   ##
=======================================
  Coverage   84.51%   84.52%           
=======================================
  Files         102      102           
  Lines       10109    10113    +4     
  Branches     2224     2224           
=======================================
+ Hits         8544     8548    +4     
  Misses       1087     1087           
  Partials      478      478           

Flag	Coverage Δ
unittests	84.30% <87.50%> (+<0.01%)	⬆️

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