feat: add faceted classification filter sidebar

[kyuchia]

Faceted Classification Filter

Adds a sidebar panel for filtering rows by classification hierarchy. This implements a faceted search / faceted navigation pattern for the classification column, allowing users to browse and filter by category/type/modifier using a tree UI, instead of scrolling through a flat list of full classification strings.

Tree structure (Neume shape-small.docx example)

neume (20)
├── tractulus (2)
│   └── episema (1)
├── punctum (1)
├── gravis (1)
├── virga (2)
│   └── episema (1)
├── oriscus (3)
│   ├── curved (1)
│   ├── flat (1)
│   └── wave (1)
├── stropha (2)
│   └── episema (1)
└── pes (9)
    ├── rotundus (2)
    │   └── 2episema (1)
    ├── quadratus (2)
    │   └── 2episema (1)
    └── quassus (5)
        ├── 2episema (1)
        ├── flexus (2)
        │   └── 23episema (1)
        └── ...

Features

• Toolbar "Filter" button (matches File/Help style) → right sidebar with tree UI
• Three-state checkboxes (all/some/none) with parent-child propagation
• Apply/Clear buttons driving Handsontable's by_value filter
• Resizable sidebar (drag left edge, 200–600px)
• Data quality warnings (⚠) for en-dash characters in classifications
• Also includes column sorting and custom dropdownMenu (removes built-in filter UI from column headers)

Files added

src/Editor/hierarchicalFilter/
├── types.ts
├── classificationTreeParser.ts
├── FilterTree.ts
├── FilterSidebar.ts
└── hierarchicalFilter.css

Testing

Tested with Neume shape-small.docx (20 rows) and SQUAREnotation-NEUMElevel.csv (39 rows, mixed categories). No console errors.