fix: restore instanceof Text and Comment in replace callback

[ashwinmridul]

Summary

• Fix exported DOM Element instanceof checks #2243 restored instanceof Element by resetting prototypes for tag/script/style nodes, but text and comment nodes were left as plain objects.
• replace callbacks that check domNode instanceof Text still failed on v6 even with matching domhandler/htmlparser2 versions.
• Apply the same prototype reset to text and comment nodes, and add a regression covering both.

Test plan

• npm test (142 tests, 100% coverage)
• replace callback: domNode instanceof Text is true for text nodes

Fixes #2256

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (0c9092c) to head (a51cbd3).

Additional details and impacted files

@@            Coverage Diff            @@
##            master     #2406   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            4         4           
  Lines          136       143    +7     
  Branches        52        54    +2     
=========================================
+ Hits           136       143    +7     

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