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/platform/ops_other.go

@@ -0,0 +1,14 @@
+//go:build !linux && !darwin && !windows
+
+package platform
+
+import "errors"
+
+// TrashName is the user-facing name of the trash.
+const TrashName = "trash"
+
+// Reveal is unsupported on this platform.
+func Reveal(string) error { return errors.New("not supported on this platform") }
+
+// Trash is unsupported on this platform.
+func Trash(string) error { return errors.New("trash not supported on this platform") }