Fix: re-export packaging symbols from platforms/_utils.py

When ruff auto-fixed imports, it removed symbols that other modules
were importing from platforms/_utils.py. Re-added all packaging imports
so they can be re-exported for backward compatibility.

This fixes import errors:
- ImportError: cannot import name 'load_pinlock'
- ImportError: cannot import name 'LockFile'
- etc.

All tests passing again (38 passed, 11 skipped).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: robtaylor

chipflow_lib/platforms/_utils.py

@@ -27,8 +27,21 @@
 from ..config_models import Config
 
 # Import packaging functionality from new module
+# These are re-exported for backward compatibility
 from ..packaging import (
-    JTAGWire,
+    Pin, PinSet, PinList, Pins,
+    PowerType, JTAGWire, PortType,
+    PowerPins, JTAGPins, BringupPins,
+    PortDesc, Interface, Component, PortMap,
+    PackageDef, Package, LockFile,
+    BasePackageDef, LinearAllocPackageDef,
+    BareDiePackageDef, QuadPackageDef,
+    GAPin, GALayout, GAPackageDef,
+    OFPin, OpenframePackageDef,
+    UnableToAllocate,
+    _count_member_pins, _allocate_pins, _linear_allocate_components,
+    _find_contiguous_sequence, _group_consecutive_items,
+    load_pinlock,
 )
 
 if TYPE_CHECKING: