fix(tui): make mac copy use pbcopy

ui-tui/src/lib/clipboard.ts

@@ -1,4 +1,4 @@
-import { execFile } from 'node:child_process'
+import { execFile, spawn } from 'node:child_process'
 import { promisify } from 'node:util'
 
 const execFileAsync = promisify(execFile)
@@ -26,3 +26,33 @@ export async function readClipboardText(
     return null
   }
 }
+
+/**
+ * Write plain text to the system clipboard.
+ *
+ * On macOS this uses `pbcopy`. On other platforms we intentionally return
+ * false for now; non-mac copy still falls back to OSC52.
+ */
+export async function writeClipboardText(
+  text: string,
+  platform: NodeJS.Platform = process.platform,
+  start: typeof spawn = spawn
+): Promise<boolean> {
+  if (platform !== 'darwin') {
+    return false
+  }
+
+  try {
+    const ok = await new Promise<boolean>(resolve => {
+      const child = start('pbcopy', [], { stdio: ['pipe', 'ignore', 'ignore'], windowsHide: true })
+
+      child.once('error', () => resolve(false))
+      child.once('close', code => resolve(code === 0))
+      child.stdin.end(text)
+    })
+
+    return ok
+  } catch {
+    return false
+  }
+}