docs: align examples README wording

[SaladSinger]

Summary

• Clarify wording for proxy vs Safe wallets in the root README.
• Normalize capitalization, punctuation, and headings for the wallet example links.
• Slightly polish the Usage text for consistency with the example READMEs.
  Notes
• Documentation-only change in src/README.md.

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Note

Improves clarity and consistency in README.md.

• Clarifies wallet terminology: proxy wallets vs Safe (Gnosis Safe) and their usage contexts
• Normalizes capitalization, punctuation, and section headings (e.g., “Proxy wallet examples”, “Safe wallet examples”)
• Polishes Usage instructions, adds inline code formatting for .env and command examples

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[SaladSinger]

This PR only updates src/README.md to clarify how proxy vs Safe wallets are used and to normalize capitalization/punctuation for the example links. No code or configuration changes.