v0.3.4

Added

• Treemap widget: zoomable hierarchical treemap rendered on canvas with hover previews, clickable path navigation, leaf selection, contextual recoloring during zoom, and constructors for direct {name, value, children} dicts, path mappings, records, or dataframes. Ported from the Svelte components in koaning/pytest-duration-insights.
• NestedTable widget: recursive expandable table showing name, summed value, and share of the root total. Shares the same hierarchy shape and from_paths / from_records / from_dataframe classmethods as Treemap.