zsh: point EDITOR at nvim, the editor we actually install

[presto8]

setup_nvim runs 'remove_package vim' and installs neovim, so $VISUAL
and $EDITOR pointed at a binary that does not exist on a freshly
provisioned machine. That also broke the 'hint: ${EDITOR:-nano} $0'
message the setup script prints when user_config has not been edited.

Update the fasd 'v' alias to match.

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🤖 Generated with Claude Code

[Copilot]

🟢 Approval recommended

The changes are minimal, consistent with the stated provisioning behavior, and remove references to a non-existent default editor binary.

Pull request overview

This PR aligns shell editor defaults and fasd’s editor alias with the editor actually installed during provisioning (neovim), preventing $VISUAL/$EDITOR from pointing to a missing vim binary and fixing editor hints that rely on $EDITOR.

Changes:

• Update $VISUAL from vim to nvim so $EDITOR resolves to an installed binary.
• Update the fasd v alias to open with nvim instead of vim.

File summaries

File	Description
prestobuntu.zsh	Switches editor environment variables and the fasd v alias to use nvim to match provisioning.

Review details

• Files reviewed: 1/1 changed files
• Comments generated: 0
• Review effort level: Lite

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