Update AI instructions to use gi create for issue management

[JonghunYu]

close #020

Summary by CodeRabbit

Release Notes

• Documentation

  • Added comprehensive "Creating Issues" section covering workflow, commands, and available options
  • Updated issue status management guidance with new procedures
  • Enhanced AI agent instructions with detailed issue-handling workflows and best practices

• Chores

  • Updated issue counter metric

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[coderabbitai]

📝 Walkthrough

Walkthrough

These changes establish standardized documentation and instructions for creating issues using the gi create command across the project. Updates were made to the issue counter (.issues/.counter incremented to 21), a new issue entry was added documenting the standardization task, and instruction files (CLAUDE.md, README.md, and cmd/init.go) were updated to include guidance on using gi create instead of manual file creation, with corresponding updates to issue status change procedures.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

🐰 Hop, hop, huzzah! The issues now flow,
With gi create commands that help them to grow,
No more scattered files in the dark,
The docs light the way like a bunny's bright spark,
Standards unite us—twenty-one strong! 🌟

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately captures the main objective of the PR—updating AI instructions to use gi create for issue management—which aligns with the changeset including updates to CLAUDE.md, README.md, cmd/init.go, and the new issue documentation.

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✨ Finishing touches

• 📝 Generate docstrings

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