feat(cli): command architecture — agents, missions, gateway-aware prdy (#158)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

packages/cli/src/commands/select-dialog.ts

@@ -0,0 +1,58 @@
+/**
+ * Interactive item selection. Uses @clack/prompts when TTY, falls back to numbered list.
+ */
+export async function selectItem<T>(
+  items: T[],
+  opts: {
+    message: string;
+    render: (item: T) => string;
+    emptyMessage?: string;
+  },
+): Promise<T | undefined> {
+  if (items.length === 0) {
+    console.log(opts.emptyMessage ?? 'No items found.');
+    return undefined;
+  }
+
+  const isTTY = process.stdin.isTTY;
+
+  if (isTTY) {
+    try {
+      const { select } = await import('@clack/prompts');
+      const result = await select({
+        message: opts.message,
+        options: items.map((item, i) => ({
+          value: i,
+          label: opts.render(item),
+        })),
+      });
+
+      if (typeof result === 'symbol') {
+        return undefined;
+      }
+
+      return items[result as number];
+    } catch {
+      // Fall through to non-interactive
+    }
+  }
+
+  // Non-interactive: display numbered list and read a number
+  console.log(`\n${opts.message}\n`);
+  for (let i = 0; i < items.length; i++) {
+    console.log(`  ${i + 1}. ${opts.render(items[i]!)}`);
+  }
+
+  const readline = await import('node:readline');
+  const rl = readline.createInterface({ input: process.stdin, output: process.stdout });
+  const answer = await new Promise<string>((resolve) => rl.question('\nSelect: ', resolve));
+  rl.close();
+
+  const index = parseInt(answer, 10) - 1;
+  if (isNaN(index) || index < 0 || index >= items.length) {
+    console.error('Invalid selection.');
+    return undefined;
+  }
+
+  return items[index];
+}