Fix references into nested placements and on asset delete (#285, #286)

Two findings from #269. A reference from a container into a placement
nested in it was dead from the start, and deleting an asset left
references to the objects it took along showing "(missing)".

- A reference is stored the way its holder shows the object. In a
  container tab that is q~x for content of a nested placement q.
- referenceCandidates translates it when the container is placed: in
  placement r, q~x becomes r~q/x. pathOfId and idOfPath in instance.ts
  do the mapping, objectChoices offers the same spelling the other way.
  The rule holds at any depth.
- Storing q/x as proposed in #285 was dropped. The container tab would
  then have had to translate its own ids.
- No migration. All projects and snapshots hold three references, none
  of them with ~ or /.
- Create container lets a reference to content of a member placement
  follow it. It was left dead before.
- Paste lets such a reference point into the copy. It kept pointing at
  the original before. Both go through the new renamedReference.
- Delete asset records what every holder shows before the cascade and
  clears every reference to an object that is gone afterwards, with
  dropReferencesToGone from #269. The row shows None, undo restores
  the references (#286).

Tests:
- Gate: 198 files, 2882 tests (2873 + 9), exit 0
- Unit object-references: 26 passed (17 + 9)
- e2e 1-17,57: 566 checks passed, 57 has +57i and +57j
- Six unit counter-probes fail between 1 and 3 tests each
- The browser counter-probe fails 57i and 57j as described in the
  issues
- e2e total 1609 is computed, not measured in a full run

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

tools/e2e/57-object-references.mjs

@@ -10,6 +10,9 @@
  * Variables tab it goes to the scene view and comes back with Take.
  *
  * Removing an object in the Container tab empties a reference a placement of it holds (#269).
+ * Inside a container the Aim can pick content of a placement nested there, and the container's
+ * placement in the scene reaches it (#285). Deleting that nested container's asset empties the
+ * reference again (#286).
  *
  * Everything it adds carries an `or57` id and goes again at the end.
  */
@@ -340,6 +343,102 @@ export async function objectReferences(t) {
     JSON.stringify({ rowBefore, tabThen, templateLeft, emptied, rowAfter, restored }),
   );
 
+  // 57i. Outer 57 holds an Aim and a placement of Inner 57 (#285). In the Container tab the Aim
+  //      picks Inner's Nest 57, stored as Outer's own view names it. Outer's placement in the scene
+  //      shows that name on its Aim, and a run reads the copy of Nest 57 there.
+  await t.showTab('scene');
+  await mutate(`
+    const p = __gm.state.project;
+    const scene = __gm.state.activeScene;
+    ${MAKE_OBJECT}
+    const sprite = p.assets.find((a) => a.type === 'sprite');
+    p.assets.push({
+      id: 'or57-inner',
+      type: 'container',
+      name: 'Inner 57',
+      props: {},
+      objects: [make('or57-i-nest', sprite.id, '', 0, 'Nest 57')],
+    });
+    p.assets.push({
+      id: 'or57-outer',
+      type: 'container',
+      name: 'Outer 57',
+      props: {},
+      objects: [
+        make('or57-o-aim', 'or57-aim', '', 0, 'Aim 57'),
+        make('or57-o-inner', 'or57-inner', '', 50, 'Inner 57'),
+      ],
+    });
+    scene.objects.push(make('or57-outer-placed', 'or57-outer', '', ${LANES.nestedReference}, 'Outer 57'));
+  `);
+  const outerTarget = () =>
+    json(
+      "__gm.state.project.assets.find((a) => a.id === 'or57-outer').objects.find((o) => o.id === 'or57-o-aim')?.overrides.target ?? null",
+    );
+  const nestName = JSON.stringify({ $object: 'or57-o-inner~or57-i-nest' });
+  await select({ kind: 'object', holderId: 'or57-outer', objectId: 'or57-o-aim' });
+  await sleep(200);
+  const outerTab = await json('__gm.tab()');
+  await press_(await json("__gm.inspectorField('target')"), 'the target field in the Container tab');
+  const inOuter = (await json('__gm.overlayTexts()')) ?? [];
+  // Nest 57 sits one level below Inner 57, so the menu indents it.
+  const nestEntry = inOuter.find((text) => text.trim() === 'Nest 57');
+  await press_(await json(`__gm.locate(${JSON.stringify(nestEntry)}, true)`), 'Nest 57 in the menu');
+  const stored = await outerTarget();
+  await t.showTab('scene');
+  const nestedAim = { kind: 'object', holderId: sceneId, objectId: 'or57-outer-placed~or57-o-aim' };
+  await select(nestedAim);
+  await sleep(200);
+  const nestedRow = { nest: await inInspector('Nest 57'), missing: await inInspector('(missing)') };
+  await shot('05-nested-reference');
+  await evaluate('__gm.state.select(null)');
+  const runFrom = t.consoleLog.length;
+  await t.play();
+  await sleep(600);
+  await stop();
+  const nestedLogged = t.consoleLog
+    .slice(runFrom)
+    .filter((line) => line.startsWith('[behavior Aim 57]'))
+    .map((line) => line.split(']').pop().trim());
+  check(
+    'a pick in the Container tab reaches into a nested placement, and the placement in the scene shows and reads it',
+    outerTab === 'container' &&
+      nestEntry !== undefined &&
+      JSON.stringify(stored) === nestName &&
+      nestedRow.nest &&
+      !nestedRow.missing &&
+      nestedLogged.includes('Nest 57'),
+    JSON.stringify({ outerTab, inOuter, stored, nestedRow, nestedLogged }),
+  );
+
+  // 57j. Deleting Inner 57 in the asset list (#286) takes its placement out of Outer 57 and empties
+  //      the Aim's reference to Nest 57 with it: the row says None, not (missing). One undo brings
+  //      both back.
+  const innerRow = await json("__gm.assetRow('or57-inner')");
+  if (!innerRow) throw new Error('Inner 57 is not in the asset list');
+  await click(innerRow.x, innerRow.y, 'right');
+  await sleep(150);
+  await press_(await json("__gm.locate('Delete…', true)"), 'Delete… in the row menu');
+  await press_(await json("__gm.locate('Delete', true)"), 'Delete in the dialog');
+  const innerLeft = await json("__gm.state.project.assets.some((a) => a.id === 'or57-inner')");
+  const cleared = await outerTarget();
+  await select(nestedAim);
+  await sleep(200);
+  const clearedRow = await targetRow();
+  await shot('06-asset-deleted');
+  await undo();
+  await sleep(150);
+  const reinstated = await outerTarget();
+  check(
+    'deleting an asset empties a reference to an object it took along, undo brings it back',
+    !innerLeft &&
+      JSON.stringify(cleared) === JSON.stringify({ $object: '' }) &&
+      clearedRow.none &&
+      !clearedRow.missing &&
+      JSON.stringify(reinstated) === nestName,
+    JSON.stringify({ innerLeft, cleared, clearedRow, reinstated }),
+  );
+
   // Clean up. Back to the scene view first: removing Aim 57 closes 57g's Variables tab, and the
   // editor then shows whatever document earlier steps left open, not the scene view.
   await t.showTab('scene');
@@ -348,6 +447,6 @@ export async function objectReferences(t) {
     const p = __gm.state.project;
     const scene = __gm.state.activeScene;
     scene.objects = scene.objects.filter((o) => !o.id.startsWith('or57-'));
-    p.assets = p.assets.filter((a) => a.id !== 'or57-aim' && a.id !== 'or57-box');
+    p.assets = p.assets.filter((a) => !a.id.startsWith('or57-'));
   `);
 }