docs: add low-effort PR examples and quality expectations document (C…

[Code-Paragon]

Summary

Adds comprehensive documentation detailing what constitutes a "low-effort" PR in aegis-contracts to set clear evaluation standards and reduce contributor friction (Closes #103).

Closes #103

Changes

• Created docs/low-effort-pr-examples.md:
  • Details 4 common anti-patterns: superficial cosmetic changes, under-tested logic, unsafe Rust (unwrap/panic), and ignored CI failures.
  • Provides clear, side-by-side examples of "Unacceptable" code vs. "Expected Alternative" code.
  • Concludes with a checklist of what a successful, high-effort PR looks like.
• Updated README.md: Linked the new guide in the Testing/Contributing section right next to the failing CI guide.

Checklist

• Tests added or updated
• Docs updated (if user-facing behavior changed)
• CI is green (all checks pass)
• Branch name follows issue/<number>-<slug> or feat/<number>-<slug>
• Cargo.lock not modified