docs: improve grammar and clarity in READMEs

[cristianoc]

No description provided.

[peter-jerry-ye-code-review]

Inconsistent capitalization of 'Codex' throughout documentation

Category
Maintainability
Code Snippet
Lines 3, 5, 8, 16, 17: Mix of 'codex', 'Codex', and 'the codex'
Recommendation
Establish consistent capitalization rules - use 'Codex' when referring to the product name and 'codex' when used as a common noun or in code contexts
Reasoning
Consistent terminology improves professional appearance and reduces confusion for users reading the documentation

Minor grammar and clarity improvements could be more comprehensive

Category
Maintainability
Code Snippet
Line 8 in README.md: 'Codex must be installed and available on your PATH.' vs README.mbt.md: 'Codex must be installed. If not, install with:'
Recommendation
Ensure both README files provide equivalent information - the .md file should include installation instructions like the .mbt.md file does
Reasoning
Documentation files should provide consistent and complete information to users regardless of which file they read first

Excellent documentation improvements with proper grammar and punctuation fixes

Category
Maintainability
Code Snippet
Multiple lines: Fixed 'To simplest way' → 'The simplest way', improved sentence structure and punctuation
Recommendation
Continue this level of attention to documentation quality in future changes
Reasoning
These changes significantly improve readability and professionalism of the documentation, making it more accessible to users

[cristianoc]

btw why are there two nearly identical readmes?