Select a range of rows with shift-click in the hierarchy (#241)

Ctrl- and shift-click only added single rows to the selection. With
many objects spread over the hierarchy, picking a run of them meant
clicking each one. Shift-click now selects everything between the
anchor and the clicked row, as in a file explorer.

- The anchor is the row last clicked without shift, plain or with
  ctrl. A second shift-click redraws the range from the same anchor.
- Ctrl+shift-click adds the range to the current selection instead
  of replacing it.
- A collapsed group inside the range brings all its members. Children
  hidden under a collapsed parent stay out, since they are not shown.
- Without an anchor from the hierarchy, the primary object picked in
  the scene view serves as anchor. With no selection at all,
  shift-click adds the single row as before.
- The range rule is a pure function in hierarchyRange.ts, so it is
  tested without a browser. HierarchyPanel keeps the anchor.

Not checked in the browser: ctrl+shift-click and the anchor taken from
the scene view. Only the code path covers them.

Tests:
- ./check.sh: 178 files, 2557 tests, CHECK EXIT 0
- e2e 1 + 52: ALL PASSED, 23 checks
- 5 new unit tests in tests/editor/hierarchy-range.test.ts
- New e2e check 52h with real clicks
- Counter-check: without the range, 52h fails with ["o2","o5"]

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/editor/hierarchy-range.test.ts

@@ -0,0 +1,57 @@
+import { describe, expect, it } from 'vitest';
+import { GroupObjectsCommand } from '../../src/core/commands/groupCommands';
+import { groupRowId, hierarchyRows } from '../../src/core/model/hierarchy';
+import { hierarchyRange } from '../../src/editor/panels/hierarchyRange';
+import { makeSpriteScene, place } from '../helpers';
+
+/** Top-level a, b, c, d, e with k under a; b and d form the group "Crates": a [b d] c e. */
+function grouped() {
+  const f = makeSpriteScene();
+  const [a, b, c, d, e] = [0, 1, 2, 3, 4].map((i) => place(f, f.spriteId, { x: i * 10, y: 0 }));
+  const k = place(f, f.spriteId, { x: 0, y: 10 }, a);
+  const group = new GroupObjectsCommand(f.sceneId, [b!, d!], 'Crates');
+  f.stack.execute(group);
+  const row = groupRowId(group.groupId);
+  const names: Record<string, string> = { [a!]: 'a', [b!]: 'b', [c!]: 'c', [d!]: 'd', [e!]: 'e', [k]: 'k' };
+  /** The row ids the panel shows with these rows unfolded. */
+  const rows = (open: string[]) =>
+    hierarchyRows(f.sceneOf(), new Set(open)).map((r) =>
+      r.kind === 'group' ? groupRowId(r.group.id) : r.object.id,
+    );
+  const range = (open: string[], anchor: string, clicked: string) =>
+    hierarchyRange(f.sceneOf(), rows(open), anchor, clicked)
+      .map((id) => names[id] ?? '?')
+      .sort()
+      .join(' ');
+  return { a: a!, b: b!, c: c!, d: d!, e: e!, k, row, range };
+}
+
+describe('Shift-click range in the hierarchy', () => {
+  it('takes every shown row between anchor and click, in either direction', () => {
+    const f = grouped();
+    expect(f.range([f.a, f.row], f.a, f.c)).toBe('a b c d k');
+    expect(f.range([f.a, f.row], f.c, f.a)).toBe('a b c d k');
+    expect(f.range([f.a, f.row], f.b, f.b)).toBe('b');
+  });
+
+  it('brings in all members of a folded group, but no children folded under a parent', () => {
+    const f = grouped();
+    expect(f.range([], f.a, f.c)).toBe('a b c d');
+  });
+
+  it('starts inside an open group and runs out of it', () => {
+    const f = grouped();
+    expect(f.range([f.row], f.d, f.e)).toBe('c d e');
+  });
+
+  it('can start or end on a group row', () => {
+    const f = grouped();
+    expect(f.range([], f.row, f.e)).toBe('b c d e');
+    expect(f.range([f.row], f.a, f.row)).toBe('a b d');
+  });
+
+  it('gives nothing when a row is not shown', () => {
+    const f = grouped();
+    expect(f.range([], f.k, f.c)).toBe('');
+  });
+});