fix(cli): update schedule provider/mode error message substring in test

The error message gained a `--mode` mention when the schedule mode flag
landed; the existing CLI integration test still asserted on the old
exact-prefix substring and broke main CI for all PR builds.

packages/cli/tests/31-loop-schedule.test.ts

@@ -118,7 +118,7 @@ try {
     assert.notStrictEqual(result.exitCode, 0, "should fail for self target with provider");
     const output = result.stdout + result.stderr;
     assert(
-      output.includes("--provider can only be used with a new-agent target"),
+      output.includes("can only be used with a new-agent target"),
       "should explain provider target mismatch",
     );
     console.log("schedule rejects provider with self target\n");