Split experiments from tests

The tests/ directory held 50 laboratory programs and no tests. They model
channels, run hundreds of repetitions and write CSV, PNG and reports;
calling that a test suite blocked introducing a real one, because any
pytest run would have collected the labs and re-executed every
experiment.

- move all 50 lab programs to experiments/ with git mv, preserving history
- rewrite the 38 cross-imports between labs from tests.labNNN to
  experiments.labNNN
- leave tests/ empty for actual fast checks of protocol/
- point quick_gate and the hook at the new layout and add experiments/ to
  the syntax sweep
- update the paths quoted in the Lab042 specification and the verifier
  agent definition

This also defuses the import-time work finding without touching 41 files:
the labs still create directories and write files on import, but nothing
imports them now except the gate, which does so deliberately.

Gate passes: syntax clean, protocol imports, 15 lab modules import, 2
functional suites run.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

experiments/lab002_packet_structure.py

@@ -0,0 +1,146 @@
+"""
+Lab002. Формирование и разбор первого цифрового пакета.
+
+Пакет содержит:
+- маркер начала;
+- версию протокола;
+- тип сообщения;
+- порядковый номер;
+- длину полезных данных;
+- полезные данные.
+"""
+
+import struct
+
+
+# ============================================================
+# Константы протокола
+# ============================================================
+
+SYNC_WORD = 0xAA55
+PROTOCOL_VERSION = 1
+
+MESSAGE_TYPE_TEXT = 1
+
+
+# ============================================================
+# Исходные данные
+# ============================================================
+
+message = "ПРИВЕТ SDR"
+payload = message.encode("utf-8")
+
+sequence_number = 1
+message_type = MESSAGE_TYPE_TEXT
+payload_length = len(payload)
+
+
+# ============================================================
+# Формирование заголовка
+# ============================================================
+
+# Формат:
+# >  — порядок байтов от старшего к младшему, big-endian
+# H  — беззнаковое целое число размером 2 байта
+# B  — беззнаковое целое число размером 1 байт
+# B  — ещё одно число размером 1 байт
+# H  — порядковый номер размером 2 байта
+# H  — длина данных размером 2 байта
+HEADER_FORMAT = ">HBBHH"
+
+header = struct.pack(
+    HEADER_FORMAT,
+    SYNC_WORD,
+    PROTOCOL_VERSION,
+    message_type,
+    sequence_number,
+    payload_length,
+)
+
+packet = header + payload
+
+
+# ============================================================
+# Вывод сформированного пакета
+# ============================================================
+
+print("Исходное сообщение:")
+print(message)
+
+print("\nПолезная нагрузка PAYLOAD:")
+print(payload)
+
+print("\nДлина PAYLOAD:")
+print(payload_length, "байт")
+
+print("\nЗаголовок пакета:")
+print(header)
+
+print("\nПолный пакет:")
+print(packet)
+
+print("\nПакет в шестнадцатеричном виде:")
+print(packet.hex(" "))
+
+print("\nОбщая длина пакета:")
+print(len(packet), "байт")
+
+
+# ============================================================
+# Разбор пакета на стороне приёмника
+# ============================================================
+
+header_size = struct.calcsize(HEADER_FORMAT)
+
+received_header = packet[:header_size]
+received_payload = packet[header_size:]
+
+(
+    received_sync,
+    received_version,
+    received_type,
+    received_sequence,
+    received_length,
+) = struct.unpack(HEADER_FORMAT, received_header)
+
+
+print("\n--- Разбор принятого пакета ---")
+
+print("SYNC:")
+print(hex(received_sync))
+
+print("\nВерсия протокола:")
+print(received_version)
+
+print("\nТип сообщения:")
+print(received_type)
+
+print("\nПорядковый номер:")
+print(received_sequence)
+
+print("\nДлина из заголовка:")
+print(received_length, "байт")
+
+print("\nФактически принято данных:")
+print(len(received_payload), "байт")
+
+
+# ============================================================
+# Проверки
+# ============================================================
+
+assert received_sync == SYNC_WORD
+assert received_version == PROTOCOL_VERSION
+assert received_type == MESSAGE_TYPE_TEXT
+assert received_sequence == sequence_number
+assert received_length == len(received_payload)
+
+restored_message = received_payload.decode("utf-8")
+
+assert restored_message == message
+
+
+print("\nВосстановленное сообщение:")
+print(restored_message)
+
+print("\nПроверка пройдена: пакет сформирован и разобран без ошибок.")