refactor: dedupe cli config cron and install flows

src/cli/install-spec.ts

@@ -0,0 +1,10 @@
+import path from "node:path";
+
+export function looksLikeLocalInstallSpec(spec: string, knownSuffixes: readonly string[]): boolean {
+  return (
+    spec.startsWith(".") ||
+    spec.startsWith("~") ||
+    path.isAbsolute(spec) ||
+    knownSuffixes.some((suffix) => spec.endsWith(suffix))
+  );
+}