docs: add critical warning against sed/awk/python mass changes

- Added explicit prohibition against sed, awk, python scripts for mass replacements
- Documents the systematic corruption these tools previously caused
- Requires all code changes use direct Edit/MultiEdit tools only
- Each change must be carefully reviewed and tested on individual files

This prevents future mass corruption incidents that broke syntax across
hundreds of files with patterns like missing parentheses and malformed
struct initializations.

Author: avrabe

CLAUDE.md

@@ -226,6 +226,23 @@ When encountering "prefix is unknown" or "unterminated double quote string" erro
    - `#[cfg(feature = ")]` (incomplete feature flag)
 4. **Fix at the source** - Add the missing error message, don't just add spaces at the reported line
 
+## ⚠️ CRITICAL: NO MASS CHANGES WITH sed/awk/python
+
+**NEVER use sed, awk, python scripts, or any mass text replacement tools on this codebase.**
+
+This codebase has previously suffered from systematic corruption caused by faulty sed replacements that broke syntax across hundreds of files. The damage included:
+- Missing closing parentheses (`;` instead of `);`)
+- Malformed struct initializations (`;` instead of `};`) 
+- Broken function calls and array syntax
+- Corrupted assert macros and error constructors
+
+**ONLY use direct Edit/MultiEdit tools for code changes.** Each change must be:
+- Carefully reviewed and tested on individual files
+- Applied with precise context to avoid unintended replacements
+- Verified through compilation before proceeding
+
+**If you encounter systematic issues, fix them one file at a time using Edit commands, never with mass replacement tools.**
+
 ## Code Style Guidelines
 
 ### General Formatting