test: H1 — root-port unplug and replug (hot-plug matrix)

The tearDownPort path, exercised for the first time with a real removal and
return: QEMU raises no root-port change events, so the bus's 250 ms
reconcile tick notices the PORTSC change alone — and it does. Reap, re-add,
rebind, second generation binds on the same port. Discrimination: against
the pre-reap manager (4a2df58~1) the case fails at the dedupe wall.

test/qemu_test.py

@@ -984,6 +984,31 @@ CASES = [
                r"[\s\S]*device-manager: delegated device \d+ to /system/drivers/usb-hid-keyboard"
                r"[\s\S]*usb-hid-keyboard: ok)",
      "fail":   r"DANOS-TEST-RESULT: FAIL"},
+    # Hot-plug matrix H1 (docs/hot-plug-matrix-plan.md): ROOT-port unplug and
+    # replug on the same port. Different teardown path than the hub case
+    # (tearDownPort, not tearDownHubDevice), and QEMU raises no port-change
+    # events for root ports — the bus's 250 ms reconcile tick must notice the
+    # PORTSC change on its own. The ordered tail (removed → reaping → delegated
+    # → ok) can only be the second generation: every boot device's ok precedes
+    # the unplug.
+    {"name": "usb-root-replug",
+     "build_case": "usb-hid",
+     "smp":    4,
+     "timeout": 150,
+     "qemu_extra": ["-device", "qemu-xhci,id=xhci2",
+                    "-device", "usb-kbd,bus=xhci2.0,port=2,id=rkbd"],
+     "qmp_sequence": [
+         {"delay": 8,  "command": "device_del", "arguments": {"id": "rkbd"}},
+         {"delay": 14, "command": "device_add",
+          "arguments": {"driver": "usb-kbd", "bus": "xhci2.0", "port": "2", "id": "rkbd2"}},
+     ],
+     "expect": r"(?s)(?=.*usb-hid-keyboard: ok \(device (\d+)\b"
+               r"[\s\S]*port \d+ disconnected"
+               r"[\s\S]*device-manager: child removed"
+               r"[\s\S]*device-manager: reaping \S*usb-hid-keyboard"
+               r"[\s\S]*device-manager: delegated device \d+ to /system/drivers/usb-hid-keyboard"
+               r"[\s\S]*usb-hid-keyboard: ok)",
+     "fail":   r"DANOS-TEST-RESULT: FAIL"},
     # The kernel VFS root (M-F): the mount table serves the initrd at /system —
     # path resolution, node status/read (an ELF magic), and directory listing,
     # asserted kernel-side.