os: improve path check with direct index access

[mertcanaltin]

Replaced String.prototype.endsWith with manual string length and index checks for performance improvements.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 88.39%. Comparing base (4d6d7d6) to head (c62d231). Report is 984 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #55434      +/-   ##
==========================================
- Coverage   88.40%   88.39%   -0.02%     
==========================================
  Files         653      653              
  Lines      187604   187596       -8     
  Branches    36119    36113       -6     
==========================================
- Hits       165849   165822      -27     
- Misses      14983    14992       +9     
- Partials     6772     6782      +10     

Files with missing lines	Coverage Δ
lib/os.js	97.34% <100.00%> (-0.01%)	:arrow_down:

... and 40 files with indirect coverage changes

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[mertcanaltin]

test/parallel/test-debugger-break.js

This test passed in my local environment, this is a flakky?

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/63249/

[juanarbol]

CI failures are unrelated to this patch

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/63355/

[nodejs-github-bot]

Landed in 81859cf01f7c0d644a80ec7bdd90f672b3d5444b