docs: add low-effort PR examples and quality expectations document (C… - #203

Summary

Adds comprehensive documentation detailing what constitutes a "low-effort" PR in aegis-dashboard to set clear evaluation standards and reduce contributor friction (Closes #148).

Closes #148

Changes

• Created docs/low-effort-pr-examples.md:
  • Details 4 common frontend anti-patterns: superficial cosmetic changes, missing Vitest coverage, unsafe state mutations (@ts-ignore/silent catches), 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 under the "Key resources for contributors" section.

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>
• pnpm-lock.yaml / package-lock.json not modified (unless dependency changes were explicitly approved)