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%

首先檢查 .github/workflows/coverage.yml、現有的 6 個測試檔案以及相依性 issue #27。檢查 26 個 hook 指令碼和目前 3/26 的測試涵蓋率，然後處理列出的 shellcheck 和測試問題。達到所述的涵蓋率目標、加入 README 徽章，並將涵蓋率設定為必要的 PR 檢查後，即視為完成。

由索引模型根據 Issue 內容生成。