refactor(workflow): convert all plugins to class/struct + factory pattern

- Python: class extending NodeExecutor + factory.py (80+ plugins)
- TypeScript: class implements NodeExecutor + factory.ts (7 groups, 116 classes)
- Go: struct with methods + factory.go (36 plugins)
- Rust: struct impl NodeExecutor trait + factory.rs (54 plugins)
- Mojo: struct + factory.mojo (11 plugins)

All package.json files now include:
- files array listing source files
- metadata.class/struct field
- metadata.entrypoint field

This enables a unified plugin loading system across all languages
with no import side effects (Spring-style DI pattern).

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

workflow/plugins/python/backend/backend_load_plugins/backend_load_plugins.py

@@ -1,50 +1,59 @@
 """Workflow plugin: load workflow plugins."""
+
 import os
 import json
-import importlib.util
+
+from ...base import NodeExecutor
 
 
-def run(runtime, inputs):
-    """Load workflow plugins from directory.
+class LoadPlugins(NodeExecutor):
+    """Load workflow plugins from directory."""
 
-    Inputs:
-        path: Path to plugins directory
-    """
-    path = inputs.get("path", "workflow/plugins/python")
+    node_type = "backend.load_plugins"
+    category = "backend"
+    description = "Load workflow plugins from directory"
 
-    if not os.path.exists(path):
-        return {"success": False, "error": f"Path not found: {path}"}
+    def execute(self, inputs, runtime=None):
+        """Load workflow plugins from directory.
 
-    plugins = {}
-    categories = []
+        Inputs:
+            path: Path to plugins directory
+        """
+        path = inputs.get("path", "workflow/plugins/python")
 
-    for category in os.listdir(path):
-        category_path = os.path.join(path, category)
-        if not os.path.isdir(category_path) or category.startswith("_"):
-            continue
+        if not os.path.exists(path):
+            return {"success": False, "error": f"Path not found: {path}"}
 
-        categories.append(category)
+        plugins = {}
+        categories = []
 
-        for plugin_name in os.listdir(category_path):
-            plugin_path = os.path.join(category_path, plugin_name)
-            if not os.path.isdir(plugin_path):
+        for category in os.listdir(path):
+            category_path = os.path.join(path, category)
+            if not os.path.isdir(category_path) or category.startswith("_"):
                 continue
 
-            package_json = os.path.join(plugin_path, "package.json")
-            if os.path.exists(package_json):
-                with open(package_json) as f:
-                    metadata = json.load(f)
-                    plugin_type = metadata.get("metadata", {}).get("plugin_type")
-                    if plugin_type:
-                        plugins[plugin_type] = {
-                            "path": plugin_path,
-                            "metadata": metadata
-                        }
+            categories.append(category)
 
-    runtime.context["plugins"] = plugins
+            for plugin_name in os.listdir(category_path):
+                plugin_path = os.path.join(category_path, plugin_name)
+                if not os.path.isdir(plugin_path):
+                    continue
 
-    return {
-        "success": True,
-        "categories": categories,
-        "plugin_count": len(plugins)
-    }
+                package_json = os.path.join(plugin_path, "package.json")
+                if os.path.exists(package_json):
+                    with open(package_json) as f:
+                        metadata = json.load(f)
+                        plugin_type = metadata.get("metadata", {}).get("plugin_type")
+                        if plugin_type:
+                            plugins[plugin_type] = {
+                                "path": plugin_path,
+                                "metadata": metadata
+                            }
+
+        runtime.context["plugins"] = plugins
+
+        return {
+            "success": True,
+            "categories": categories,
+            "plugin_count": len(plugins)
+        }

workflow/plugins/python/backend/backend_load_plugins/factory.py

@@ -0,0 +1,7 @@
+"""Factory for LoadPlugins plugin."""
+
+from .backend_load_plugins import LoadPlugins
+
+
+def create():
+    return LoadPlugins()

workflow/plugins/python/backend/backend_load_plugins/package.json

@@ -6,8 +6,11 @@
   "license": "MIT",
   "keywords": ["backend", "workflow", "plugin", "loader"],
   "main": "backend_load_plugins.py",
+  "files": ["backend_load_plugins.py", "factory.py"],
   "metadata": {
     "plugin_type": "backend.load_plugins",
-    "category": "backend"
+    "category": "backend",
+    "class": "LoadPlugins",
+    "entrypoint": "execute"
   }
 }