fix(patterns): correct non-blocking timing and blink off phase

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/all.py

@@ -184,6 +184,36 @@ def test_pattern_smoke():
         ctx.tick_for_ms(120)
 
 
+def test_patterns_do_not_use_blocking_sleep():
+    pattern_dir = "patterns"
+    offenders = []
+    try:
+        files = os.listdir(pattern_dir)
+    except OSError:
+        raise AssertionError("patterns directory is missing")
+
+    for filename in files:
+        if not filename.endswith(".py") or filename in ("__init__.py", "main.py"):
+            continue
+        path = pattern_dir + "/" + filename
+        try:
+            with open(path, "r") as f:
+                src = f.read()
+        except OSError:
+            offenders.append(filename + " (unreadable)")
+            continue
+
+        if (
+            "utime.sleep(" in src
+            or "utime.sleep_ms(" in src
+            or "time.sleep(" in src
+            or "time.sleep_ms(" in src
+        ):
+            offenders.append(filename)
+
+    assert not offenders, "blocking sleep found in patterns: %s" % ", ".join(offenders)
+
+
 def test_default_requires_existing_preset():
     ctx = _TestContext()
     _process_message(ctx, {"v": "1", "default": "missing"})
@@ -242,6 +272,7 @@ def run_all():
         test_preset_edit_sanitization,
         test_colour_conversion_and_transition,
         test_pattern_smoke,
+        test_patterns_do_not_use_blocking_sleep,
         test_default_requires_existing_preset,
         test_default_targets_gate_by_device_name,
         test_save_and_load_roundtrip,