feat: allow subpath imports that start with #/

[hybrist]

Port of the equivalent change in nodejs.

See: nodejs/node#60864

Summary

Matches latest behavior of the resolution in nodejs (upcoming v25 release).

What kind of change does this PR introduce?

A new feature: supporting more subpath imports.

Did you add tests for your changes?

Tests are included.

Does this PR introduce a breaking change?

No breaking changes, turns error cases into successful resolutions.

If relevant, what needs to be documented once your changes are merged or what have you already documented?

[alexander-akait]

Thanks

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.12%. Comparing base (79e2961) to head (2386713).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #468      +/-   ##
==========================================
- Coverage   93.13%   93.12%   -0.01%     
==========================================
  Files          45       45              
  Lines        2155     2153       -2     
  Branches      654      653       -1     
==========================================
- Hits         2007     2005       -2     
  Misses        119      119              
  Partials       29       29              

Flag	Coverage Δ
integration	93.12% <ø> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.