feat: add Replace and SetByPath methods to Node for in-place updates

[TheApeMachine]

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 30.83333% with 83 lines in your changes missing coverage. Please review.
✅ Project coverage is 51.10%. Comparing base (59be92f) to head (1a8b66c).
⚠️ Report is 83 commits behind head on main.

Files with missing lines	Patch %	Lines
ast/node.go	30.83%	59 Missing and 24 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #956      +/-   ##
==========================================
- Coverage   51.86%   51.10%   -0.77%     
==========================================
  Files         127      170      +43     
  Lines       10893    14265    +3372     
==========================================
+ Hits         5650     7290    +1640     
- Misses       4920     6561    +1641     
- Partials      323      414      +91     

Flag	Coverage Δ
arm	42.76% <30.83%> (?)
macos-latest	43.94% <35.23%> (?)
ubuntu-24.04-arm	42.74% <30.83%> (?)
ubuntu-latest	49.62% <35.23%> (?)
x86	49.62% <35.23%> (?)

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