add smp-retry test for the AP wake retry path

Test hook forces the first wake to fail; the case asserts every core still comes online. Verified it fails when retry is disabled.

src/kernel/main.zig

@@ -269,6 +269,12 @@ fn bringUpSecondaries() void {
     arch.setTrampolinePage(ap_trampoline_page);
     arch.setSecondaryEntry(scheduler.secondaryMain); // where a woken core joins the run loop
 
+    // Test hook: the smp-retry case forces the first wake to fail, so the retry below
+    // must still bring every core online. Inert in a normal build (test_case is null).
+    if (build_options.test_case) |tc| {
+        if (std.mem.eql(u8, tc, "smp-retry")) arch.testFailNextWakes(1);
+    }
+
     log.print("\ndanos: bringing up {d} application processor(s)\n", .{cores.len - 1});
     const max_wake_attempts = 3; // a core that misses the first INIT-SIPI-SIPI gets retried
     for (cores[1..], 1..) |core, index| {