This happens when you load the VS Code and immediately try to work. It takes a good 5+ mins sometimes for the VS Code to load the plugins like Salesforce CLI and SFDX.
To not have this issue, update your VS code and extensions to the latest version and restart it.
https://salesforce.stackexchange.com/questions/357082/not-seeing-sfdx-commands-in-vs-code
Issue has been resolved once I install the extension 'Salesforce CLI Integration' into VScode . I am bit confuse how it was worked early , may be I mistakenly uninstall 'Salesforce CLI Integration' . But anyhow good news is now its working and also able to run/execute Apex script from my VScode IDE.
拡張機能「Salesforce CLI Integration」を VScode にインストールすると、問題は解決しました。初期段階でどのように機能していたのか少し混乱しています。おそらく、誤って「Salesforce CLI Integration」をアンインストールしたのかもしれません。 VScode IDE から Apex スクリプトを実行/実行します。