Add no-heredoc instructions to prevent terminal file corruption

[garrettsiegel]

Adds instructions to prevent file corruption caused by terminal heredoc operations in VS Code Copilot.

Problem

Heredoc syntax (cat << EOF) in VS Code's integrated terminal causes file corruption due to:

• Tab completion interference
• Quote/backtick escaping failures
• Exit code 130 interruptions

Solution

This instruction file tells Copilot to always use file editing tools instead of terminal redirections for any file creation or modification.

Applies to all files (**) since the issue affects any agent writing files via terminal.

[Copilot]

Pull request overview

This PR adds a new instruction file to prevent file corruption caused by heredoc operations in VS Code's integrated terminal when using Copilot.

Changes:

• Adds no-heredoc.instructions.md instruction file that enforces the use of file editing tools instead of terminal heredoc operations (cat << EOF, etc.)