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/tui/live_test.go

@@ -0,0 +1,71 @@
+package tui
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/andydixon/mapsize/internal/inventory"
+	"github.com/andydixon/mapsize/internal/scan"
+)
+
+// TestLiveScanRendering renders, navigates, filters and resizes while the
+// scanner mutates the inventory. Run with -race to verify the locking
+// discipline.
+func TestLiveScanRendering(t *testing.T) {
+	root := t.TempDir()
+	for i := range 30 {
+		d := filepath.Join(root, fmt.Sprintf("d%02d", i), "sub")
+		if err := os.MkdirAll(d, 0o755); err != nil {
+			t.Fatal(err)
+		}
+		for j := range 40 {
+			os.WriteFile(filepath.Join(d, fmt.Sprintf("f%d.log", j)), make([]byte, (i+1)*(j+1)*100), 0o644)
+		}
+	}
+	start := func(ctx context.Context) (*scan.Scanner, *inventory.Tree, error) {
+		s, err := scan.Start(ctx, root, scan.Options{Workers: 4, ChunkSize: 3})
+		if err != nil {
+			return nil, nil, err
+		}
+		return s, s.Tree, nil
+	}
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	s, tr, err := start(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	m := newModel(Options{Start: start}, s, tr, cancel)
+	sizes := [][2]int{{120, 40}, {80, 24}, {200, 60}, {45, 12}}
+	deadline := time.After(20 * time.Second)
+	for i := 0; ; i++ {
+		send(m, size(sizes[i%len(sizes)][0], sizes[i%len(sizes)][1]), tickMsg(time.Now()))
+		send(m, key([]string{"right", "down", "left", "up"}[i%4]))
+		if i%5 == 0 {
+			send(m, key("tab"))
+		}
+		if i == 3 {
+			m.search.ed.set("ext = log")
+			m.queryChanged()
+			send(m, m.applyFilter()())
+		}
+		m.dirty = true
+		m.View()
+		select {
+		case <-s.Done():
+			send(m, scanDoneMsg{s})
+			m.View()
+			if m.scanning {
+				t.Fatal("scan should be finished")
+			}
+			return
+		case <-deadline:
+			t.Fatal("scan did not finish")
+		default:
+		}
+	}
+}