fix(install_cli): sudo: command not found on certain machines

[cabljac]

Firebase Studio integration was reportedly getting the following:

This PR:

• euid/sudo aware installs: if not root and install dir isn’t writable, use sudo when available; otherwise fall back to ~/.local/bin. Uninstall path uses the same logic.
• Correct install detection: separated desired target from existing binary; only treat as installed if an executable exists, preventing false “corrupted/installed” when GENKIT_BINARY is set.
• Repro + validation: added .github/workflows/repro-install-cli.yml to reproduce the sudo-less failure and confirm the fixed script installs locally; verified locally with act.

[Copilot]

Pull Request Overview

This PR fixes an installation issue where the Genkit CLI install script fails on machines without sudo privileges. The fix implements fallback installation logic that uses ~/.local/bin when sudo is not available or when the user cannot write to the global installation directory.

• Adds smart installation logic that checks for sudo availability and directory write permissions
• Fixes installation detection to properly identify existing executables vs environment variables
• Adds GitHub Actions workflow to reproduce and validate the sudo-less installation scenario

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

[pavelgj]

@cabljac were you able to repro this in Firebase Studio? You can just create a workspace in https://idx.google.com

IDX is nix. I think in their setup the problem might be that you don't get root access at all (can't sudo nor su). /usr/local/bin also doesn't exist and you can't create it.

I wonder if we need a "local=true" install option that writes the binary to $HOME/.local/bin instead of /usr/local/bin?