fix(cli): avoid duplicate Zsh positional completion

packages/cli/test/completions.test.ts

@@ -0,0 +1,15 @@
+import { expect, test } from "bun:test"
+import path from "node:path"
+
+test("zsh completion does not define the first positional twice", async () => {
+  const proc = Bun.spawn([process.execPath, path.join(import.meta.dir, "../src/index.ts"), "--completions", "zsh"], {
+    stdout: "pipe",
+    stderr: "pipe",
+  })
+  const output = await new Response(proc.stdout).text()
+  const error = await new Response(proc.stderr).text()
+
+  expect(await proc.exited, error).toBe(0)
+  expect(output).toContain("'1:command:->command'")
+  expect(output).not.toContain("':Directory to start OpenCode in:'")
+})