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/test/test_assert_true/factory.py

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

workflow/plugins/python/test/test_assert_true/package.json

@@ -1,13 +1,16 @@
 {
   "name": "@metabuilder/test_assert_true",
   "version": "1.0.0",
-  "description": "test_assert_true plugin",
+  "description": "Assert that a value is true",
   "author": "MetaBuilder",
   "license": "MIT",
   "keywords": ["test", "workflow", "plugin"],
   "main": "test_assert_true.py",
+  "files": ["test_assert_true.py", "factory.py"],
   "metadata": {
     "plugin_type": "test.assert_true",
-    "category": "test"
+    "category": "test",
+    "class": "TestAssertTrue",
+    "entrypoint": "execute"
   }
 }

workflow/plugins/python/test/test_assert_true/test_assert_true.py

@@ -1,23 +1,32 @@
 """Workflow plugin: assert value is true."""
 
+from ...base import NodeExecutor
 
-def run(_runtime, inputs):
+
+class TestAssertTrue(NodeExecutor):
     """Assert that a value is true."""
-    value = inputs.get("value")
-    message = inputs.get("message", "")
 
-    passed = value is True
+    node_type = "test.assert_true"
+    category = "test"
+    description = "Assert that a value is true"
+
+    def execute(self, inputs, runtime=None):
+        """Assert that a value is true."""
+        value = inputs.get("value")
+        message = inputs.get("message", "")
+
+        passed = value is True
+
+        if not passed:
+            error_msg = f"Assertion failed: {message}" if message else "Assertion failed"
+            error_msg += f"\n  Expected: True\n  Actual: {value}"
+            return {
+                "passed": False,
+                "error": error_msg,
+                "value": value
+            }
 
-    if not passed:
-        error_msg = f"Assertion failed: {message}" if message else "Assertion failed"
-        error_msg += f"\n  Expected: True\n  Actual: {value}"
         return {
-            "passed": False,
-            "error": error_msg,
+            "passed": True,
             "value": value
         }
-
-    return {
-        "passed": True,
-        "value": value
-    }