chore: clean up plans folder and add main branch protection

[dnim]

• Remove completed plans (fix-pause-audio, feat-config, vrt)
• Normalize remaining plans to template format
• Update ui-themes plan to reflect current codebase
• Add pre-commit hook to prevent direct commits to main

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.08%. Comparing base (3cb8f8a) to head (28225b2).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #32   +/-   ##
=======================================
  Coverage   84.08%   84.08%           
=======================================
  Files           9        9           
  Lines         685      685           
  Branches      176      176           
=======================================
  Hits          576      576           
  Misses        109      109           

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