Bump pygments to 2.20.0

[EhteshamSid]

These packages have security fixes available:

• pygments 2.19.2 -> 2.20.0 (CVE-2026-4539)

Bumped each one to the minimum safe version.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.731%. Comparing base (785d77f) to head (a26c412).

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #3158       +/-   ##
=============================================
- Coverage   87.793%   87.731%   -0.062%     
=============================================
  Files          105       105               
  Lines         8143      8143               
  Branches      1290      1290               
=============================================
- Hits          7149      7144        -5     
- Misses         687       692        +5     
  Partials       307       307               

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[EhteshamSid]

The bandit failure is pre-existing and unrelated to the guide/requirements.txt change