Migrate web UI from Streamlit to NiceGUI

Replace the Streamlit-based UI (app.py + tab_*.py) with an event-driven
NiceGUI implementation. This eliminates 135 session_state accesses,
35 st.rerun() calls, and the ui_reset_token hack. Key changes:

- Add main.py as NiceGUI entry point with sidebar, tabs, and file navigation
- Add state.py with AppState dataclass replacing st.session_state
- Add tab_batch_ng.py (batch processor with blur-binding, VACE calc)
- Add tab_timeline_ng.py (history tree with graphviz, batch delete)
- Add tab_raw_ng.py (raw JSON editor)
- Add tab_comfy_ng.py (ComfyUI monitor with polling timer)
- Remove Streamlit dependency from utils.py (st.error → logger.error)
- Remove Streamlit mock from tests/test_utils.py

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tab_raw_ng.py

@@ -0,0 +1,74 @@
+import copy
+import json
+
+from nicegui import ui
+
+from state import AppState
+from utils import save_json, get_file_mtime, KEY_HISTORY_TREE, KEY_PROMPT_HISTORY
+
+
+def render_raw_editor(state: AppState):
+    data = state.data_cache
+    file_path = state.file_path
+
+    ui.label(f'Raw Editor: {file_path.name}').classes('text-h6')
+
+    hide_history = ui.checkbox(
+        'Hide History (Safe Mode)',
+        value=True,
+    )
+
+    @ui.refreshable
+    def render_editor():
+        # Prepare display data
+        if hide_history.value:
+            display_data = copy.deepcopy(data)
+            display_data.pop(KEY_HISTORY_TREE, None)
+            display_data.pop(KEY_PROMPT_HISTORY, None)
+        else:
+            display_data = data
+
+        try:
+            json_str = json.dumps(display_data, indent=4, ensure_ascii=False)
+        except Exception as e:
+            ui.notify(f'Error serializing JSON: {e}', type='negative')
+            json_str = '{}'
+
+        text_area = ui.textarea(
+            'JSON Content',
+            value=json_str,
+        ).classes('w-full font-mono').props('outlined rows=30')
+
+        ui.separator()
+
+        def do_save():
+            try:
+                input_data = json.loads(text_area.value)
+
+                # Merge hidden history back in if safe mode
+                if hide_history.value:
+                    if KEY_HISTORY_TREE in data:
+                        input_data[KEY_HISTORY_TREE] = data[KEY_HISTORY_TREE]
+                    if KEY_PROMPT_HISTORY in data:
+                        input_data[KEY_PROMPT_HISTORY] = data[KEY_PROMPT_HISTORY]
+
+                save_json(file_path, input_data)
+
+                data.clear()
+                data.update(input_data)
+                state.last_mtime = get_file_mtime(file_path)
+
+                ui.notify('Raw JSON Saved Successfully!', type='positive')
+                render_editor.refresh()
+
+            except json.JSONDecodeError as e:
+                ui.notify(f'Invalid JSON Syntax: {e}', type='negative')
+            except Exception as e:
+                ui.notify(f'Unexpected Error: {e}', type='negative')
+
+        ui.button('Save Raw Changes', icon='save', on_click=do_save).props(
+            'color=primary'
+        ).classes('w-full')
+
+    hide_history.on_value_change(lambda _: render_editor.refresh())
+    render_editor()