Remove unused code and add dead-code convention to CLAUDE.md

- Remove unused imports: QImage (items), QTransform, QGraphicsItem (scene)
- Remove unused signal: zoom_requested (scene)
- Add convention: delete all unused code immediately, no dead code allowed

Author: JE-Chen

CLAUDE.md

@@ -84,6 +84,7 @@ python -m pybreeze                              # launch the IDE
 - Exception hierarchy: all custom exceptions inherit from `ITEException`
 - Logging: use `pybreeze_logger` from `pybreeze.utils.logging.logger`
 - Plugin API: `register_programming_language()` and `register_natural_language()` from `je_editor.plugins`
+- Delete all unused code — do not leave dead imports, unreachable functions, commented-out blocks, or unused variables. If code is not called by any execution path, remove it entirely. No `# TODO: remove later` or `_old_` prefixes — delete immediately.
 
 ## Security
 

pybreeze/pybreeze_ui/diagram_editor/diagram_items.py

@@ -8,7 +8,6 @@
     QBrush,
     QColor,
     QFont,
-    QImage,
     QPainter,
     QPainterPath,
     QPen,

pybreeze/pybreeze_ui/diagram_editor/diagram_scene.py

@@ -4,8 +4,8 @@
 from enum import Enum, auto
 
 from PySide6.QtCore import QPointF, Qt, Signal
-from PySide6.QtGui import QColor, QPen, QPixmap, QTransform, QUndoStack
-from PySide6.QtWidgets import QGraphicsItem, QGraphicsLineItem, QGraphicsScene, QMenu
+from PySide6.QtGui import QColor, QPen, QPixmap, QUndoStack
+from PySide6.QtWidgets import QGraphicsLineItem, QGraphicsScene, QMenu
 
 from pybreeze.pybreeze_ui.diagram_editor.diagram_commands import DiagramSnapshotCommand
 from pybreeze.pybreeze_ui.diagram_editor.diagram_items import (
@@ -42,7 +42,6 @@ class DiagramScene(QGraphicsScene):
 
     mode_changed = Signal(ToolMode)
     item_count_changed = Signal()
-    zoom_requested = Signal(float)  # emitted when scene wants to change zoom
 
     def __init__(self, parent=None):
         super().__init__(parent)