track: Code coverage reporting implementation

## Overview
Track the implementation and improvement of code coverage reporting for all hook scripts.

## Current Status
- ✅ Coverage workflow created (`.github/workflows/coverage.yml`)
- ✅ kcov integration configured
- ⚠️ Coverage currently at 0% (no hooks passing tests)

## Goals
- [ ] Fix hook scripts to pass shellcheck
- [ ] Achieve 50% coverage
- [ ] Achieve 80% coverage target
- [ ] Add coverage badge to README
- [ ] Integrate coverage checks in PR reviews

## Tracking Metrics
- Current coverage: 0%
- Target coverage: 80%
- Number of hooks tested: 3/26
- Number of test files: 6

## Related PRs
- Initial coverage setup: (this commit)

## Dependencies
- Depends on #27 (test coverage for all hooks)
- Blocks v1.0.0 release

## Action Items
1. Fix shellcheck errors in hook scripts
2. Update tests to handle hook script issues
3. Add coverage badge to README
4. Configure coverage as required PR check

## Milestone
Test Coverage 80%

首先检查 .github/workflows/coverage.yml、现有的 6 个测试文件以及依赖项 issue #27。检查 26 个 hook 脚本和当前 3/26 的测试覆盖率，然后处理列出的 shellcheck 和测试问题。达到所述的覆盖率目标、添加 README 徽章，并将覆盖率配置为必需的 PR 检查后，即视为完成。

由索引模型根据 Issue 内容生成。