build(deps): update actions/checkout action to v6.0.3

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
actions/checkout	action	patch	v6.0.2 → v6.0.3

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Release Notes

actions/checkout (actions/checkout)

v6.0.3

Compare Source

• Fix checkout init for SHA-256 repositories by @​yaananth in #​2439
• fix: expand merge commit SHA regex and add SHA-256 test cases by @​yaananth in #​2414

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[claude]

actions/checkout を v6.0.2 から v6.0.3 へ更新するパッチアップデートです。SHA df4cb1c069e1874edd31b4311f1884172cec0e10 は公式の v6.0.3 タグと一致しており、SHA ピンも正しく更新されています。変更内容は SHA-256 リポジトリ対応のバグ修正 (actions/checkout#2414, actions/checkout#2439) のみで、本リポジトリへの機能的影響はありません。安全にマージできます。

Review metadata

• Reviewed commit: 59656b1
• PR: #142
• kyosei: 3.5.0
• kyosei-action: 2.2.0
• Claude Code: 2.1.150
• Model: claude-opus-4-7
• Execution: GitHub Actions (run)