docs(ja-JP): translate plain text code blocks to Japanese

Translate English prose inside plain text code blocks (```text, ```)
across ja-JP documentation to Japanese, following the same approach
as PR #753 (zh-CN translation).

Translated content includes:
- Output template labels and status messages
- Folder tree inline comments
- CLI workflow descriptions
- Error/warning message examples
- Commit message templates and PR title examples

Technical identifiers, file paths, and actual code remain untranslated.

docs/ja-JP/rules/git-workflow.md

@@ -3,9 +3,9 @@
 ## コミットメッセージフォーマット
 
 ```
-<type>: <description>
+<type>: <説明>
 
-<optional body>
+<任意の本文>
 ```
 
 タイプ: feat, fix, refactor, docs, test, chore, perf, ci