git-issue-startlisted

# Implement Issue Skill Automate the workflow from GitHub Issue information retrieval, label validation, branch creation, to Plan Mode transition. ## Steps ### Step 1: Determine Issue Number - If `$ARGUMENTS` is specified as a number, use that Issue number - If not specified or not a number, ask the user for the Issue number: ```text 対応するIssueの番号を教えてください。 ``` - If a clear number cannot be determined from the user's response, exit with an error. Do not guess or make ambiguous interpretations: ```text エラー: Issue番号を特定できませんでした。数値で指定してください。 ``` ### Step 2: Fetch Issue Information 1. Fetch Issue information with `gh issue view <Issue number> --json number,title,body,labels,state` 2. If the command fails (no Issue exists for the given number): - Check if it exists as a PR with `gh pr view <Issue number>`, and if it's a PR, display the following and exit: ```text エラー: #XX はPRです。Issueの番号を指定してください。 ``` - If it's not a PR either, display the following and exit: ```text エラー: Issue #XX は存在しません。 ``` 3. If `state` is not `OPEN` → warn with "このIssueは既にクローズされています" and exit 4. Display the fetched information in the following format: ```text ## Issue #XX: <タイトル> ラベル: <ラベル一覧> <本文> ``` ### Step 3: Label Validation Validate the following based on the "Mandatory Issue Labels" section in the shared development conventions (`conventions.md`): 1. **Type label**: Verify that one of `bug`, `feature`, `enhancement`, `docume