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/utils/utils_not/factory.py

@@ -0,0 +1,7 @@
+"""Factory for Not plugin."""
+
+from .utils_not import Not
+
+
+def create():
+    return Not()

workflow/plugins/python/utils/utils_not/package.json

@@ -1,13 +1,16 @@
 {
   "name": "@metabuilder/utils_not",
   "version": "1.0.0",
-  "description": "utils_not plugin",
+  "description": "Negate a boolean value",
   "author": "MetaBuilder",
   "license": "MIT",
   "keywords": ["utils", "workflow", "plugin"],
   "main": "utils_not.py",
+  "files": ["utils_not.py", "factory.py"],
   "metadata": {
     "plugin_type": "utils.not",
-    "category": "utils"
+    "category": "utils",
+    "class": "Not",
+    "entrypoint": "execute"
   }
 }

workflow/plugins/python/utils/utils_not/utils_not.py

@@ -1,7 +1,16 @@
 """Workflow plugin: boolean not."""
 
+from ...base import NodeExecutor
 
-def run(_runtime, inputs):
+
+class Not(NodeExecutor):
     """Negate a boolean value."""
-    value = inputs.get("value")
-    return {"result": not bool(value)}
+
+    node_type = "utils.not"
+    category = "utils"
+    description = "Negate a boolean value"
+
+    def execute(self, inputs, runtime=None):
+        """Negate a boolean value."""
+        value = inputs.get("value")
+        return {"result": not bool(value)}