ci: add commit message helper tools to enforce conventional commits

[Copilot]

commitlint CI was failing due to commits not following Conventional Commits format (e.g., "Initial plan" → errors on missing type and subject).

Changes

Interactive commit helper

• pnpm commit - menu-driven interface for creating valid commit messages
• Validates input, supports optional scope, shows preview

Git hook template

• .husky/prepare-commit-msg - auto-populates template on git commit
• Shows format, valid types, examples

Documentation

• COMMIT_GUIDELINES.md - format spec, all commit types, examples, tool usage
• Updated README.md and CONTRIBUTING.md with references

Usage

# Interactive (recommended)
pnpm commit

# Template-assisted
git commit  # Opens editor with template

# Manual
git commit -m "feat: add user authentication"

All new commits in this PR follow conventional format and pass commitlint validation.

Original prompt

引用: https://github.com/chris-han/CopilotKit/actions/runs/21988769015/job/63529888979#step:8:1
✖ found 2 problems, 0 warnings

2026-02-13T13:36:27.0680918Z ✔ found 0 problems, 0 warnings
2026-02-13T13:36:27.0681668Z ⧗ input: Initial plan
2026-02-13T13:36:27.0682233Z ✖ subject may not be empty [subject-empty]
2026-02-13T13:36:27.0682767Z ✖ type may not be empty [type-empty]
2026-02-13T13:36:27.0682970Z
2026-02-13T13:36:27.0683151Z ✖ found 2 problems, 0 warnings
2026-02-13T13:36:27.0683742Z ⓘ Get help: https://github.com/conventional-changelog/commitlint/#what-is-commitlint
2026-02-13T13:36:27.0684106Z
2026-02-13T13:36:27.0842416Z ##[error]Process completed with exit code 1.
fix it with script generation or default value

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