refactor: 迁移 cli/_ops/ 到 ops/, 按类别保持 dev/files/media/system 分类

将 src/pyflowx/cli/_ops/ 整体迁移至 src/pyflowx/ops/, 与 cli/ 平级
(工具函数非 CLI 专属, 可被 YAML 任务编排通用引用). 分类保持不变:
dev (git/pip/bump/autofmt), files (date/level/back/zip),
media (pdf/screenshot), system (ls/pack/ssh).

同步更新 15 个引用文件 (yaml_loader + 14 个测试) 的 import 路径,
README 模块结构表与 test_registry docstring.

src/pyflowx/ops/dev.py

@@ -93,12 +93,10 @@ _INIT_VERSION_PATTERN = re.compile(
 PACKAGE_DIR = "packages"
 REQUIREMENTS_FILE = "requirements.txt"
 
-_PROTECTED_PACKAGES: frozenset[str] = frozenset(
-    {
-        "pyflowx",
-        "bitool",
-    }
-)
+_PROTECTED_PACKAGES: frozenset[str] = frozenset({
+    "pyflowx",
+    "bitool",
+})
 
 
 # ============================================================================