fix(tests): make housekeep subcommand test platform-agnostic

The test was failing on Windows because the help text shows
"mutx.exe housekeep" instead of "mutx housekeep". Updated to
check for platform-independent parts of the usage message.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: aaronbassett

tests/cli_housekeep_test.rs

@@ -79,5 +79,8 @@ fn test_housekeep_requires_subcommand() {
     cmd.arg("housekeep")
         .assert()
         .failure()
-        .stderr(predicate::str::contains("Usage: mutx housekeep <COMMAND>"));
+        // Check for key parts of the usage message, avoiding platform-specific binary name
+        .stderr(predicate::str::contains("housekeep <COMMAND>"))
+        .stderr(predicate::str::contains("locks"))
+        .stderr(predicate::str::contains("backups"));
 }