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/tests.zig

@@ -72,6 +72,8 @@ pub fn run(case: []const u8, boot_info: *const BootInfo) void {
         smpTest();
     } else if (eql(case, "smp-stress")) {
         stressTest();
+    } else if (eql(case, "smp-retry")) {
+        smpRetryTest();
     } else if (eql(case, "fault-ud")) {
         faultInvalidOpcode();
     } else if (eql(case, "fault-pf")) {
@@ -570,6 +572,20 @@ fn stressTest() void {
     result();
 }
 
+/// Retry: `main` forced the first AP wake attempt to fail (arch.testFailNextWakes),
+/// so a core missed its first INIT-SIPI-SIPI. The boot retry must have brought it back
+/// anyway — every enumerated core should be online. If retry were broken, that core
+/// would be parked and the count would fall short.
+fn smpRetryTest() void {
+    log("DANOS-TEST-BEGIN: smp-retry\n", .{});
+    const total = platform.cpus().len;
+    const online = sched.onlineCount();
+    log("DANOS-RETRY: {d}/{d} cores online after a forced first-wake failure\n", .{ online, total });
+    check("multiple cores enumerated (run with -smp)", total >= 2);
+    check("retry brought every core online despite a failed first wake", online == total);
+    result();
+}
+
 fn faultInvalidOpcode() void {
     log("DANOS-TEST-BEGIN: fault-ud\n", .{});
     asm volatile ("ud2");