[refactor] reorganize devtools test nodes into modules (#6020)

## Summary

Refactored monolithic devtools node definitions into organized module
structure for better maintainability and separation of concerns.

## Changes

- **What**: Split 700+ line `dev_nodes.py` into modular structure under
`tools/devtools/nodes/` with categorized files: `errors.py`,
`inputs.py`, `models.py`, `remote.py`
- **Dependencies**: None

## Review Focus

Module import structure and ensure all node registrations are properly
preserved in the consolidated mappings.

**Before:**
```
tools/devtools/
├── __init__.py
└── dev_nodes.py (738 lines)
```

**After:**
```
tools/devtools/
├── __init__.py
├── dev_nodes.py (65 lines - imports only)
└── nodes/
    ├── __init__.py (consolidated mappings)
    ├── errors.py (error/debug nodes)
    ├── inputs.py (input/widget nodes)
    ├── models.py (model/patch nodes)
    └── remote.py (remote/combo nodes)
```

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6020-refactor-reorganize-devtools-test-nodes-into-modules-2896d73d365081e89efef7e88ca8fee3)
by [Unito](https://www.unito.io)

tools/devtools/nodes/__init__.py

@@ -0,0 +1,93 @@
+from __future__ import annotations
+
+from .errors import (
+    DeprecatedNode,
+    ErrorRaiseNode,
+    ErrorRaiseNodeWithMessage,
+    ExperimentalNode,
+    NODE_CLASS_MAPPINGS as errors_class_mappings,
+    NODE_DISPLAY_NAME_MAPPINGS as errors_display_name_mappings,
+)
+from .inputs import (
+    LongComboDropdown,
+    NodeWithBooleanInput,
+    NodeWithDefaultInput,
+    NodeWithForceInput,
+    NodeWithOptionalComboInput,
+    NodeWithOptionalInput,
+    NodeWithOnlyOptionalInput,
+    NodeWithOutputList,
+    NodeWithSeedInput,
+    NodeWithStringInput,
+    NodeWithUnionInput,
+    NodeWithValidation,
+    NodeWithV2ComboInput,
+    SimpleSlider,
+    NODE_CLASS_MAPPINGS as inputs_class_mappings,
+    NODE_DISPLAY_NAME_MAPPINGS as inputs_display_name_mappings,
+)
+from .models import (
+    DummyPatch,
+    LoadAnimatedImageTest,
+    ObjectPatchNode,
+    NODE_CLASS_MAPPINGS as models_class_mappings,
+    NODE_DISPLAY_NAME_MAPPINGS as models_display_name_mappings,
+)
+from .remote import (
+    MultiSelectNode,
+    NodeWithOutputCombo,
+    RemoteWidgetNode,
+    RemoteWidgetNodeWithControlAfterRefresh,
+    RemoteWidgetNodeWithParams,
+    RemoteWidgetNodeWithRefresh,
+    RemoteWidgetNodeWithRefreshButton,
+    NODE_CLASS_MAPPINGS as remote_class_mappings,
+    NODE_DISPLAY_NAME_MAPPINGS as remote_display_name_mappings,
+)
+
+NODE_CLASS_MAPPINGS = {
+    **errors_class_mappings,
+    **inputs_class_mappings,
+    **remote_class_mappings,
+    **models_class_mappings,
+}
+
+NODE_DISPLAY_NAME_MAPPINGS = {
+    **errors_display_name_mappings,
+    **inputs_display_name_mappings,
+    **remote_display_name_mappings,
+    **models_display_name_mappings,
+}
+
+__all__ = [
+    "DeprecatedNode",
+    "DummyPatch",
+    "ErrorRaiseNode",
+    "ErrorRaiseNodeWithMessage",
+    "ExperimentalNode",
+    "LoadAnimatedImageTest",
+    "LongComboDropdown",
+    "MultiSelectNode",
+    "NodeWithBooleanInput",
+    "NodeWithDefaultInput",
+    "NodeWithForceInput",
+    "NodeWithOptionalComboInput",
+    "NodeWithOptionalInput",
+    "NodeWithOnlyOptionalInput",
+    "NodeWithOutputCombo",
+    "NodeWithOutputList",
+    "NodeWithSeedInput",
+    "NodeWithStringInput",
+    "NodeWithUnionInput",
+    "NodeWithValidation",
+    "NodeWithV2ComboInput",
+    "ObjectPatchNode",
+    "RemoteWidgetNode",
+    "RemoteWidgetNodeWithControlAfterRefresh",
+    "RemoteWidgetNodeWithParams",
+    "RemoteWidgetNodeWithRefresh",
+    "RemoteWidgetNodeWithRefreshButton",
+    "SimpleSlider",
+    "NODE_CLASS_MAPPINGS",
+    "NODE_DISPLAY_NAME_MAPPINGS",
+]