pci-bus registers and reports what it scans (M19.2)

Each function is registered under the bridge with the config-space slice
and BARs sized by the same all-ones probe the kernel uses — byte-for-byte
equal descriptors, so the idempotent register returns the kernel's
existing node ids during coexistence instead of duplicating the tree.
The bridge gained the 16-bit io_port aperture that functions' I/O BARs
need to pass containment. Reports carry the registered device_id, and
the pci-scan scenario drills a forced restart: kill the enumerator after
its reports, watch the respawn re-scan, and assert the broker's PCI node
count never grew. The usb-restart test trigger is pinned to the xHCI
reporter (pci-bus racing it to two reports used to steal the kill).
Harness hardening: failing cases preserve their serial logs; the heavy
scenarios run at 150s.

system/services/device-manager/device-manager.zig

@@ -108,6 +108,7 @@ var manager_endpoint: runtime.ipc.Handle = 0;
 var test_restart_mode = false;
 var test_usb_restart_mode = false;
 var test_usb_killed = false;
+var test_pci_restart_mode = false;
 var test_kill_pid: u32 = 0;
 var test_kill_due_ns: u64 = 0;
 
@@ -400,13 +401,32 @@ fn onChildAdded(message: []const u8, reply: []u8, sender: u32) usize {
     }
     const report_reply = protocol.ReportReply{ .status = status };
     @memcpy(reply[0..@sizeOf(protocol.ReportReply)], std.mem.asBytes(&report_reply));
+    if (test_pci_restart_mode and !test_usb_killed) {
+        if (driverByProcess(sender)) |driver| {
+            if (std.mem.eql(u8, driver.name(), "pci-bus") and childCountOf(sender) >= 3) {
+                // The pci restart drill: kill the enumerator after it has
+                // reported; the respawn must re-register without duplicates
+                // (M19.0 idempotence, proven end to end by pci-scan).
+                test_usb_killed = true;
+                test_kill_pid = sender;
+                test_kill_due_ns = system.clock() + 1_000_000_000;
+                _ = system.timerOnce(manager_endpoint, 1100);
+            }
+        }
+    }
     if (test_usb_restart_mode and !test_usb_killed and childCountOf(sender) >= 2) {
-        // Delayed, not immediate: the device-list scenario's subscriber needs a
-        // window to enumerate and subscribe before the events start.
-        test_usb_killed = true;
-        test_kill_pid = sender;
-        test_kill_due_ns = system.clock() + 2_000_000_000;
-        _ = system.timerOnce(manager_endpoint, 2100);
+        // Only the xHCI reporter is the drill's victim — pci-bus also reports
+        // now, and whichever finishes second must not trigger the kill.
+        if (driverByProcess(sender)) |driver| {
+            if (std.mem.eql(u8, driver.name(), "usb-xhci-bus")) {
+                // Delayed, not immediate: the device-list scenario's subscriber
+                // needs a window to enumerate and subscribe before the events.
+                test_usb_killed = true;
+                test_kill_pid = sender;
+                test_kill_due_ns = system.clock() + 2_000_000_000;
+                _ = system.timerOnce(manager_endpoint, 2100);
+            }
+        }
     }
     return @sizeOf(protocol.ReportReply);
 }
@@ -476,6 +496,7 @@ pub fn main(init: runtime.process.Init) void {
     if (init.arguments.get(1)) |mode| {
         test_restart_mode = std.mem.eql(u8, mode, "test-restart");
         test_usb_restart_mode = std.mem.eql(u8, mode, "test-usb-restart");
+        test_pci_restart_mode = std.mem.eql(u8, mode, "test-pci-restart");
     }
     runtime.service.run(protocol.message_maximum, .{
         .service = .device_manager,