Add Bubble Tea TUI with interactive treemap

Cell canvas renderer with frame cache and a perceptual 256-colour
quantizer; responsive geometry (large/medium/small/too-small);
squarified treemap with nested previews, LOD grouping, category
colouring and adaptive labels; spatial arrow navigation with stable
NodeID selection; zoom and breadcrumbs; modal system (info, help,
confirm, save); list, file-type, top-N, scan-info, duplicate and
comparison views; live search/filter; mouse support; move-to-trash.

internal/inventory/tree.go

@@ -51,6 +51,7 @@ const (
 	FlagAllocUnknown                   // platform cannot report allocated size
 	FlagBrokenLink                     // symlink target does not exist
 	FlagHardlinked                     // regular file with link count > 1
+	FlagDeleted                        // moved to trash from the UI
 )
 
 // Node is one filesystem object. Sizes are own sizes; Tot* fields are