test: e2e firmware update, and restarts told apart by boot time

With --reboot, a restore of the radio alone brings it back as it was:
on a board without Ethernet it read the radio from the wrong place.

--firmware <firmware.bin> updates the device through /updateFirmware and
checks it still runs a minute later, after it marks the update good.

wait_for_restart compared uptimes, so a test run right after another
restart could see more uptime than before and fail.  It compares boot
times, and waits while the device hasn't restarted yet.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

test/e2e/test_update.py

@@ -0,0 +1,48 @@
+"""A firmware update through /updateFirmware, as the web UI sends it.
+
+Pass --firmware with a firmware.bin built for the device's chip, e.g.
+.pio/build/esp32s3/firmware.bin.  The device must have an OTA slot: the
+release builds do, the C5, C6 and debug builds don't.
+"""
+import time
+
+import pytest
+
+from proto_client import run_sync
+from test_routes import auth, upload
+from test_settings import boot_time, wait_for_restart
+
+# The new firmware is marked good once it has run this long with the network
+# up; a reset before then boots the old one (docs/adr/0003-pioarduino-idf55.md).
+PROVEN_AFTER_S = 60
+
+
+@pytest.fixture
+def firmware(request):
+    path = request.config.getoption("--firmware")
+    if not path:
+        pytest.skip("updates the device's firmware: pass --firmware <firmware.bin>")
+    with open(path, "rb") as f:
+        return f.read()
+
+
+def test_an_update_restarts_on_the_new_firmware_and_stays(host, token, connect, schema, firmware):
+    c = connect(schema=schema.hash)
+    _, frames, _ = run_sync(c)
+    booted = boot_time(schema, frames)
+    c.close()
+
+    status, _, body = upload(host, "/updateFirmware", auth(token), file=firmware)
+    assert status == 200, body
+    wait_for_restart(host, token, schema, booted)
+
+    # Past the point where it is marked good it is still running, and hasn't
+    # restarted on the old firmware.
+    c = connect(schema=schema.hash)
+    _, frames, _ = run_sync(c)
+    restarted = boot_time(schema, frames)
+    c.close()
+    time.sleep(PROVEN_AFTER_S + 10)
+    c = connect(schema=schema.hash)
+    _, frames, _ = run_sync(c)
+    assert abs(boot_time(schema, frames) - restarted) < 5, "the device restarted again"