Add multi-selection to glyph catalog filters

[kostyafarber]

Problem

The glyph catalog supports only one category or subcategory filter at a time. Its disclosure and selection interactions are also coupled: clicking a category chevron can select the whole category while opening it. This prevents users from combining useful catalog scopes and makes expanding the hierarchy change the current filter unexpectedly.

Expected outcome

Catalog categories and subcategories support familiar list multi-selection. Selected scopes combine as a union, while disclosure controls only expand or collapse the hierarchy.

Acceptance criteria

• Clicking a category or subcategory label without modifiers replaces the current catalog filter selection.
• Command-click on macOS and Control-click elsewhere toggles an individual category or subcategory in the filter selection.
• Shift-click selects a contiguous range of sibling categories or sibling subcategories from the selection anchor.
• Glyphs matching any selected category or subcategory are shown.
• Selecting a top-level category replaces selected child scopes beneath it; selecting a child scope replaces its selected parent.
• Clicking a category chevron only expands or collapses that category and does not change filter selection.
• Clicking “All” clears category and subcategory filter selection.
• Contiguous selected rows render as one continuous block, while hovered unselected rows retain their gap and rounded treatment.