feat(notstrap): add new-machine bootstrap orchestrator

crates/notstrap/src/prereqs.rs

@@ -0,0 +1,25 @@
+use anyhow::Result;
+use which::which;
+
+pub struct Prereq {
+    pub cmd: &'static str,
+    pub install_hint: &'static str,
+}
+
+const PREREQS: &[Prereq] = &[
+    Prereq { cmd: "nu",   install_hint: "brew install nushell  OR  nix-env -iA nixpkgs.nushell" },
+    Prereq { cmd: "sops", install_hint: "brew install sops  OR  nix-env -iA nixpkgs.sops" },
+    Prereq { cmd: "age",  install_hint: "brew install age   OR  nix-env -iA nixpkgs.age" },
+];
+
+pub fn check_prerequisites() -> Result<()> {
+    let missing: Vec<&Prereq> = PREREQS.iter().filter(|p| which(p.cmd).is_err()).collect();
+    if missing.is_empty() {
+        return Ok(());
+    }
+    eprintln!("Missing required tools:\n");
+    for p in &missing {
+        eprintln!("  {} — {}", p.cmd, p.install_hint);
+    }
+    anyhow::bail!("{} prerequisite(s) missing", missing.len())
+}