chore: Refactor visual mode hooks

[TrevorBurnham]

Description of changes:

This CR refactors the three visual mode hooks (useCurrentMode, useDensityMode, and useReducedMotion) to reduce duplication. All behavior should be identical.

This change reduces raw bundle size by 444 bytes, and should make maintenance for these functions a bit easier.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.77%. Comparing base (54c5ad9) to head (7ede906).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #171      +/-   ##
==========================================
- Coverage   98.78%   98.77%   -0.01%     
==========================================
  Files          36       36              
  Lines         904      900       -4     
  Branches      255      241      -14     
==========================================
- Hits          893      889       -4     
  Misses         11       11              

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