fix: factorization dropping operations when paths share a string prefix

[fnoopv]

fix #45

This fixes issue #45, where enabling Factorize() could produce an incomplete patch.

Root cause:
the move validation logic used a plain string prefix check to determine whether the source path was a proper prefix of the destination path. This was too broad for JSON Pointers and incorrectly treated sibling paths such as /key/b and /key/bb as a parent/child relationship.

As a result, a valid factorization candidate could be rejected and the add operation was dropped, leaving an incomplete patch.

Changes:

• replace the plain strings.HasPrefix check with a JSON Pointer-aware proper prefix check that requires a segment boundary
• add a fixture regression case for the reported scenario
• add a direct Go regression test covering both non-factorized and factorized behavior

With this change:

• without Factorize(), the diff remains remove + add
• with Factorize(), the diff is correctly reduced to a move from /key/b to /key/bb

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.93%. Comparing base (65fb3ba) to head (31743f2).

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #46      +/-   ##
==========================================
+ Coverage   94.89%   94.93%   +0.04%     
==========================================
  Files          12       12              
  Lines         979      987       +8     
==========================================
+ Hits          929      937       +8     
  Misses         30       30              
  Partials       20       20              

Flag	Coverage Δ
unittests	94.93% <100.00%> (+0.04%)	⬆️

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[wI2L]

@fnoopv Thank you for your contribution.