Fix a few parser consistency things, and populate a line offset table for position reporting

[FollowTheProcess]

Summary

[codecov]

Codecov Report

❌ Patch coverage is 84.61538% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.9%. Comparing base (694c60b) to head (dd90784).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/syntax/parser/parser.go	81.2%	6 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #182     +/-   ##
=======================================
+ Coverage   77.7%   77.9%   +0.1%     
=======================================
  Files         27      27             
  Lines       1970    1978      +8     
=======================================
+ Hits        1531    1541     +10     
+ Misses       338     336      -2     
  Partials     101     101             

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