Add SiloMetadataEditor widget that opens in an MDI subwindow when the
user double-clicks the Metadata node in the Silo tree. Supports editing
lifecycle state, tags (add/remove chips), and schema-defined fields with
type-inferred widgets (QCheckBox, QDoubleSpinBox, QLineEdit).
Changes:
- silo_viewers.py: SiloMetadataEditor with dirty tracking, Save/Reset
buttons, unsaved-changes close guard, and tag chip management
- silo_objects.py: mark_dirty()/is_dirty()/clear_dirty() on proxy
- kc_format.py: fix entries=None before hooks; _metadata_save_hook
writes dirty RawContent back to silo/ cache on document save
Closes#39
Add document tree infrastructure that creates Silo metadata nodes when
a .kc file is opened. Nodes appear under a "Silo" group and represent
the silo/ ZIP directory entries (manifest, metadata, history, etc.).
New files:
- silo_objects.py: SiloViewerObject proxy with Transient properties
- silo_viewproviders.py: SiloViewerViewProvider with icon stubs
- silo_tree.py: SiloTreeBuilder with conditional node creation
- silo_document.py: SiloDocumentObserver singleton + registration
Modified files:
- kc_format.py: pre_reinject hook system for silo/ entry mutation
- InitGui.py: 600ms timer registration for document observer
- CMakeLists.txt: install list for 4 new Python files
Closes#37
