Fix nested ref resolution for remote documents

[andreyyudin]

Nested $ref values inside remote documents were resolved using the root spec’s index/path instead of the referenced document’s context, which breaks relative refs inside remote files.

Changes

• Resolve nested refs using the referenced document’s index/path context when configured.
• Cache compiled JSONPath expressions to reduce repeated parse/alloc overhead during node lookups and tighten timeout handling.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.52%. Comparing base (7b6048a) to head (5da73a0).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #505      +/-   ##
==========================================
+ Coverage   99.50%   99.52%   +0.01%     
==========================================
  Files         190      190              
  Lines       23013    23063      +50     
==========================================
+ Hits        22900    22953      +53     
+ Misses         68       67       -1     
+ Partials       45       43       -2     

Flag	Coverage Δ
unittests	99.52% <100.00%> (+0.01%)	⬆️

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[daveshanley]

Did you use AI for this?

The fix is down in the guts of the system, which is highly complex! I am surprised at the intricacy of the fix - it smells like AI to me.... amirite?

[daveshanley]

Solid work!

[andreyyudin]

Thank you for approving! Yes, AI help was utilised, though even with that it took quite a bit of involvement. This is a rather complex issue and there should be another PR coming for Vacuum itself. Our team has encountered a problem with Spectral handling ref resolution on a large input - it would simply run out of memory or hang. We switched to Vacuum as it was producing a result, yet after investigating more this issue was found.