Tests against lost bytes in dense frames

- test_nano: every hex digit of B data is one drawDots() call, never single
  drawPixel() calls (the slow path that broke dense images in 2.19.2)
- tools/display_smoke_test.py: all yellow, a dense image and a checkerboard
  in live mode on the real display; fails on any frame check problem (wrong
  image, no answer, Nano restart, ERR reply)

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

tools/display_smoke_test.py

@@ -0,0 +1,105 @@
+"""Checks on the real display that the Nano gets every frame right, also very dense ones.
+Run it after changes to the Nano firmware, the driver (lib/BROSE9323) or the frames.
+
+    python tools/display_smoke_test.py [ESP32 address, default 10.1.1.198]
+
+It shows a few test images in live mode (all yellow, a dense image, a checkerboard), waits
+for the frame check of each (the Nano's checksum of what it received) and then goes back
+to normal. It fails when the frame check found a wrong image, a missing answer, a Nano
+restart or an ERR reply (e.g. "Line too long": lost bytes). This is the speed test the PC
+tests can't do: with 2.19.2 the Nano drew dense images slower than they arrived, which
+broke all yellow. The dots flip for about 20 s. Only the Python standard library is used.
+"""
+
+import json
+import sys
+import time
+import urllib.error
+import urllib.request
+
+ESP = 'http://' + (sys.argv[1] if len(sys.argv) > 1 else '10.1.1.198')
+W, H, ROW_BYTES = 84, 19, 11
+CHECK_TIMEOUT = 20  # s: the ESP asks every 3 s at most, the answer takes up to 2 s
+COUNTERS = ('mismatches', 'no_reply', 'errors', 'restarts', 'repairs')
+
+
+def request(path, body=None):
+    data = None if body is None else json.dumps(body).encode()
+    req = urllib.request.Request(ESP + path, data=data, headers={'Content-Type': 'application/json'})
+    try:
+        with urllib.request.urlopen(req, timeout=30) as r:
+            return json.loads(r.read())
+    except urllib.error.HTTPError as e:
+        sys.exit('%s: %s' % (path, e.read().decode(errors='replace')))
+
+
+def image(dot):
+    """Bitmap hex (logic/bitmap_format.h: rows of 11 bytes, MSB = left dot) of dot(x, y)."""
+    out = []
+    for y in range(H):
+        for i in range(ROW_BYTES):
+            v = 0
+            for k in range(8):
+                x = i * 8 + k
+                if x < W and dot(x, y):
+                    v |= 0x80 >> k
+            out.append('%02x' % v)
+    return ''.join(out)
+
+
+TESTS = [
+    ('all yellow', image(lambda x, y: True)),
+    # About 90 % of the dots, scattered: like the panda bitmap that failed
+    ('dense image', image(lambda x, y: (x * 7 + y * 13) % 11 != 0)),
+    ('checkerboard', image(lambda x, y: (x + y) % 2 == 0)),
+]
+
+
+def link():
+    return request('/api/status')['nano_link']
+
+
+def answered(counts):
+    return counts['checks'] + counts['mismatches'] + counts['no_reply']
+
+
+def main():
+    status = request('/api/status')
+    if not status['power_enabled']:
+        sys.exit('The Power switch is off (Home Assistant): live mode is not possible')
+    effect_s = request('/api/settings')['drive']['effect_time'] / 1000
+    start = link()
+    print('Firmware %s, frame check before: %s' % (status['version'], start))
+
+    failed = False
+    try:
+        for name, data in TESTS:
+            before = link()
+            request('/api/live', {'data': data})
+            deadline = time.time() + CHECK_TIMEOUT
+            now = before
+            while answered(now) == answered(before) and time.time() < deadline:
+                time.sleep(0.5)
+                now = link()
+            if answered(now) == answered(before):
+                print('%-13s no frame check within %d s' % (name, CHECK_TIMEOUT))
+                failed = True
+                continue
+            bad = {c: now[c] - before[c] for c in COUNTERS if now[c] != before[c]}
+            print('%-13s %s' % (name, 'ok' if not bad else 'FAILED %s %s' % (bad, now['last_error'])))
+            failed |= bool(bad)
+            time.sleep(effect_s + 1)  # let it finish flipping, so each image can be seen
+    finally:
+        request('/api/live/stop', {})
+
+    end = link()
+    bad = {c: end[c] - start[c] for c in COUNTERS if end[c] != start[c]}
+    if bad:
+        print('Frame check after: %s, last error: %s' % (bad, end['last_error']))
+        failed = True
+    print('FAILED' if failed else 'All frames arrived right')
+    sys.exit(1 if failed else 0)
+
+
+if __name__ == '__main__':
+    main()