feat(pybot): bot4cj 的 Python 迁移版（.mt 解析 + 硬件驱动 + 插件系统）

- parser: FSM 解析器与仓颉版逐语义对齐，修 S01/S02/S04/Q05
- robot/hardvars: 六类硬件变量工厂，修 r.cj:911 重名 FIXME、Q07 倒序释放
- plugin: Python 插件替代 Lua 桥接，修 S07 三级路径查找
- hd: i2c(每fd锁 Q03/S06)/spi/servo/kalman/mpu6050(S05/Q06)/speaker(S03 实声)
- modules: PCA9685 与 Lua 版逐字节对齐；ADS1115 重写(experimental)；ADS1256 空桩
- tests: 42 项 pytest 全绿（Mock 总线 journal 断言）
- CLI: --dry-run / --test roundtrip / --verbose；运行时零第三方依赖

pybot/tests/test_plugin.py

@@ -0,0 +1,49 @@
+"""插件加载器测试：三级路径查找(S07) / 缺失报错 / 实例隔离"""
+
+import pytest
+
+from pybot import plugin
+
+
+def test_find_builtin_module():
+    """包内置 modules/ 能找到 PCA9685"""
+    path = plugin.find_module("PCA9685")
+    assert path.name == "PCA9685.py"
+    assert path.parent.name == "modules"
+
+
+def test_plugin_not_found():
+    with pytest.raises(plugin.PluginNotFound) as ei:
+        plugin.find_module("NoSuchDevice")
+    assert "NoSuchDevice" in str(ei.value)
+    assert "modules" in str(ei.value)       # 报错含搜索路径
+
+
+def test_env_path_priority(tmp_path, monkeypatch):
+    """$PYBOT_MODULES_PATH 优先于包内置目录"""
+    (tmp_path / "PCA9685.py").write_text(
+        "def build(ctx): return {'from': 'env'}\n"
+        "def call(ctx): return {}\n"
+        "def destroy(ctx): return {}\n", encoding="utf-8")
+    monkeypatch.setenv("PYBOT_MODULES_PATH", str(tmp_path))
+    assert plugin.find_module("PCA9685") == tmp_path / "PCA9685.py"
+    mod = plugin.load_module("PCA9685")
+    assert mod.build({}) == {"from": "env"}
+
+
+def test_missing_protocol_function(tmp_path, monkeypatch):
+    """插件缺 build/call/destroy 任一函数即拒绝加载"""
+    (tmp_path / "Broken.py").write_text(
+        "def build(ctx): return {}\n", encoding="utf-8")
+    monkeypatch.setenv("PYBOT_MODULES_PATH", str(tmp_path))
+    with pytest.raises(plugin.PluginNotFound):
+        plugin.load_module("Broken")
+
+
+def test_independent_instances():
+    """每次加载新模块实例：模块级全局状态互不共享（对齐 Lua 每设备状态机）"""
+    a = plugin.load_module("SPI")
+    b = plugin.load_module("SPI")
+    assert a is not b
+    a._fd = 42
+    assert b._fd == -1