Replace the manual tokenizer and recursive descent parser with a PEG
grammar using the pest library.
This migration involves introducing a formal grammar in formula.pest and
updating the parser implementation to utilize the generated Pest parser
with a tree-walking approach to construct the AST.
The change introduces a stricter requirement for identifiers: multi-word
identifiers must now be enclosed in pipe quotes (e.g., |Total Revenue|) and
are no longer accepted as bare words.
Tests have been updated to reflect the new parsing logic, remove
tokenizer-specific tests, and verify the new pipe-quoting and escape
semantics.
BREAKING CHANGE: Multi-word identifiers now require pipe-quoting (e.g. |Total Revenue|) and
are no longer accepted as bare words.
Co-Authored-By: fiddlerwoaroof/git-smart-commit (gemma-4-31B-it-UD-Q4_K_XL.gguf)
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