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/string/string_trim/string_trim.py

@@ -1,16 +1,20 @@
 """Workflow plugin: trim whitespace from string."""
 
+from ...base import NodeExecutor
 
-def run(_runtime, inputs):
+
+class StringTrim(NodeExecutor):
     """Trim whitespace from string."""
-    text = inputs.get("text", "")
-    mode = inputs.get("mode", "both")
 
-    if mode == "start":
-        result = text.lstrip()
-    elif mode == "end":
-        result = text.rstrip()
-    else:
-        result = text.strip()
+    node_type = "string.trim"
+    category = "string"
+    description = "Trim whitespace from string"
 
-    return {"result": result}
+    def execute(self, inputs, runtime=None):
+        value = str(inputs.get("value", inputs.get("text", "")))
+        mode = inputs.get("mode", "both")
+        if mode == "start":
+            return {"result": value.lstrip()}
+        elif mode == "end":
+            return {"result": value.rstrip()}
+        return {"result": value.strip()}