Pick an existing collider or rigidbody from the object menu (#222)

"Add collider" and "Add rigidbody" could only create a fresh asset.
Reusing one meant creating a copy by hand, and a new box collider
never matched the sprite it was added to.

- "Add collider…" and "Add rigidbody…" open a second menu at the same
  spot: a search field, "Create new …", a separator, then every asset
  of that kind sorted by name. Enter takes the first match.
- An existing asset is placed as a shared child, not copied. An asset
  the object already carries is greyed out.
- The rule for when the entries are available lives in one place in
  the collider commands. An object without a resolvable asset is
  greyed out again, as with the old canAddCollider.
- "Fit to sprite" in the menu of a placed collider sizes it to its
  sprite and centres it (position 0,0, z kept) as one undo step.
- Fit writes overrides of that placement, not the asset, because a
  collider can now sit on several sprites. A value equal to the asset
  value clears the override instead.
- Fit removes the collider's own scale, swaps width and height near
  90 degrees and gives a circle the radius that fits (min/2). It is
  greyed out for polygon and frame outlines and off a sprite.
- Menu has no submenus, so a second menu opens instead, similar to
  "Add Component" in Unity. That costs one click more than before.

Tests:
- ./check.sh: 152 files, 2234 tests, CHECK EXIT 0 (before 151/2228).
- 6 new unit tests in tests/core/collider-parts.test.ts.
- 3 new e2e checks in 08a: submenu with search and greying, an
  existing collider via search and Enter, Fit on oc2.
- 09, 40 and 41 follow the new labels.
- e2e 1-16,39-41 on the final build: ALL PASSED, 596 checks.
- Counter-checks: no greying, existing asset ignored and fit without
  centring each fail at their own check. Breaking the override rule
  fails 2 unit tests.
- CI confirmed 1345 checks at 2cf7202 (task 265). New total 1348,
  calculated.

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

tools/e2e/08-colliders.mjs

@@ -33,14 +33,35 @@ export async function colliders(t) {
     stop,
   } = t;
 
-  // 8a. Right-click the red crate → "Add collider": a collider asset sized like the crate
-  //     (100×60) is placed as its child at the centre, selected and drawn in the overlay. The
-  //     seed already gives both crates a "Crate collider" child (oc1/oc2), so the added one is
-  //     undone again to keep exactly one collider per body for the checks below.
+  // 8a. Right-click the red crate → "Add collider…" opens a second, searchable menu (#222): a new
+  //     collider or one the project has, the shared "Crate collider" the crate wears greyed out.
+  //     "Create new collider" places a collider asset sized like the crate (100×60) as its child at
+  //     the centre, selected and drawn in the overlay. The seed already gives both crates a
+  //     "Crate collider" child (oc1/oc2), so the added one is undone again to keep exactly one
+  //     collider per body for the checks below.
   const objectsBefore = (await objects()).length;
-  const redRow = await locate('Red crate');
-  await click(redRow.x, redRow.y, 'right');
-  await clickText('Add collider');
+  const assetCount = () => json('__gm.state.project.assets.length');
+  const colliderMenuOf = async (id) => {
+    await evaluate('__gm.hierarchyExpandAll()');
+    const row = await inView(t, '__gm.leftColumn().objects', `__gm.hierarchyRow(${JSON.stringify(id)})`);
+    await click(row.x, row.y, 'right');
+    await clickText('Add collider…');
+  };
+  await colliderMenuOf('o1');
+  const pickRows = await json('__gm.menuRows()');
+  const pickEnabled = await json('__gm.menuEnabled()');
+  await typeText('crate');
+  const searched = ((await json('__gm.menuRows()')) ?? []).filter(Boolean);
+  await press('Escape');
+  check(
+    'Add collider… offers a new or an existing collider, searchable; one the crate wears is greyed out',
+    JSON.stringify(pickRows) === JSON.stringify(['Create new collider', null, 'Crate collider']) &&
+      JSON.stringify(pickEnabled) === JSON.stringify([true, null, false]) &&
+      JSON.stringify(searched) === JSON.stringify(['Crate collider']),
+    JSON.stringify({ pickRows, pickEnabled, searched }),
+  );
+  await colliderMenuOf('o1');
+  await clickText('Create new collider');
   const s = await state();
   const colObj = s.selection?.kind === 'object' ? await object(s.selection.objectId) : null;
   const colAsset = colObj ? await asset(colObj.assetId) : null;
@@ -58,6 +79,22 @@ export async function colliders(t) {
   );
   check('collider inspector shows the shape menu', Boolean(await evaluate(`__gm.locate('Box')`)));
   await shot('21-collider');
+
+  // The blue crate takes that new collider as it is: its name typed and Enter place it below the
+  // crate, no second asset made.
+  const assetsWithNew = await assetCount();
+  await colliderMenuOf('o2');
+  if (colAsset) await typeText(colAsset.name);
+  await press('Enter');
+  const sShared = await state();
+  const shared = sShared.selection?.kind === 'object' ? await object(sShared.selection.objectId) : null;
+  const assetsAfterShare = await assetCount();
+  check(
+    'picking an existing collider places it below the blue crate without a new asset',
+    shared?.parentId === 'o2' && shared.assetId === colAsset?.id && assetsAfterShare === assetsWithNew,
+    JSON.stringify({ shared, assetsWithNew, assetsAfterShare }),
+  );
+  if (shared) await undo();
   await undo();
   const colliderAssetGone = colAsset ? !(await asset(colAsset.id)) : false;
   check(
@@ -65,6 +102,26 @@ export async function colliders(t) {
     (await objects()).length === objectsBefore && colliderAssetGone,
   );
 
+  // 8a-iii. "Fit to sprite" on a collider (#222): the blue crate's collider, pushed aside and
+  //         narrowed, covers its 140-wide crate again and sits centred – which is how the seed has it.
+  await mutate(`
+    const oc2 = __gm.state.activeScene.objects.find(o => o.id === 'oc2');
+    oc2.position = { x: 30, y: 12, z: 0 };
+    oc2.overrides = { width: 90 };`);
+  const oc2Row = await inView(t, '__gm.leftColumn().objects', `__gm.hierarchyRow('oc2')`);
+  await click(oc2Row.x, oc2Row.y, 'right');
+  const colliderRows = ((await json('__gm.menuRows()')) ?? []).filter(Boolean);
+  if (colliderRows.includes('Fit to sprite')) await clickText('Fit to sprite');
+  else await press('Escape');
+  const fitted = await object('oc2');
+  check(
+    'Fit to sprite sizes the collider like its sprite and centres it on the sprite',
+    JSON.stringify(fitted?.overrides) === JSON.stringify({ width: 140 }) &&
+      fitted.position.x === 0 &&
+      fitted.position.y === 0,
+    JSON.stringify({ colliderRows, fitted }),
+  );
+
   // 8b. Wire "On collision enter → Log(other)" into the Mover (owner = red crate) and play with
   //      the crates overlapping: the log names the blue crate exactly once (enter, not stay),
   //      and colliders are not rendered in play mode.

tools/e2e/09-containers.mjs

@@ -302,7 +302,9 @@ export async function containers(t) {
     const before = (await objects()).length;
     const noticeNow = await notice();
     await click(row.x, row.y, 'right');
-    await clickText('Add collider');
+    await clickText('Add collider…');
+    // An enabled entry opens the second menu (#222); a disabled one leaves the first standing.
+    if (await has('Create new collider')) await clickText('Create new collider');
     await press('Escape');
     return { added: (await objects()).length - before, notice: await noticeNow() };
   };

tools/e2e/40-tilemap.mjs

@@ -771,8 +771,8 @@ export async function tilemap(t) {
   const OBJECT_MENU = [
     'Select asset',
     'Open asset',
-    'Add collider',
-    'Add rigidbody',
+    'Add collider…',
+    'Add rigidbody…',
     'Create container',
     'Unpack container',
     'Unparent (move to top level)',

tools/e2e/41-physics.mjs

@@ -125,7 +125,9 @@ export async function physics(t) {
     const row = await inView(t, '__gm.leftColumn().objects', `__gm.hierarchyRow(${JSON.stringify(id)})`);
     const before = (await objects()).length;
     await click(row.x, row.y, 'right');
-    await clickText('Add rigidbody');
+    await clickText('Add rigidbody…');
+    // An enabled entry opens the second menu (#222); a disabled one leaves the first standing.
+    if (await has('Create new rigidbody')) await clickText('Create new rigidbody');
     await press('Escape');
     const s = await state();
     const selected = s.selection?.kind === 'object' ? await object(s.selection.objectId) : null;