Ask a foreign manifest whether it can be loaded, not how it was wired

The performance harness runs the candidate's benchmark against a
baseline checkout, so the candidate's validator reads a manifest built
by an older commit. #535 put a rule about the CURRENT build into that
shared validator — the panel graph must not contain the card facade —
and it is false of every build before #535 by construction. The
candidate then refused to load any older baseline: all nine performance
profiles went red at once on the same step, the stable release gate
withheld `houseplan-card.js` from the published v1.75.0, and none of it
was about speed.

assertBundleManifest now answers only the loader's question: paths
exist, nothing is duplicated, graphs reference listed assets, sizes add
up. The topology of the current build moves to assertOwnBundleTopology,
called from bundle-sync.mjs, which materializes our own dist, and from
the unit test that reads dist/houseplan-assets.json. Neither ever looks
at a foreign tree.

Reproduced end to end, not only in a unit: a v1.74.0 worktree built with
its own code, then `node demo/benchmark_large_house.mjs
--target-root=<baseline>` from this tree. Before the change it stops
with «initial panel graph must contain its own stable entry only»; after
it, the profile is captured.

Issue: #537
User-Visible: no

scripts/mutation-gate.mjs

@@ -3124,6 +3124,25 @@ const MUTANT_DEFINITIONS = [
       replace: '      void panelEntry; // mutant: cached panel keeps its static shared-chunk import',
     }],
   },
+  {
+    id: 'manifest-loader-judges-current-topology',
+    guard: 'node --test --test-name-pattern="#537 loader-side validation" '
+      + 'test/bundle-assets.test.mjs',
+    because: 'the loader-side validator also reads FOREIGN manifests — the performance harness '
+      + 'runs the candidate against a baseline checkout — so a rule about how the CURRENT build '
+      + 'is wired makes the candidate refuse to load any older baseline. That is what turned all '
+      + 'nine performance profiles red at once and withheld an asset from a published stable '
+      + 'release (#537)',
+    patches: [{
+      file: 'scripts/bundle-tree.mjs',
+      find: '  if (!initialPanel.includes(PANEL_ENTRY)) {\n'
+        + '    throw new Error(`${label}: initial panel graph must contain its own stable entry`);\n'
+        + '  }',
+      replace: '  if (initialPanel.includes(CARD_ENTRY) || !initialPanel.includes(PANEL_ENTRY)) {\n'
+        + '    throw new Error(`${label}: initial panel graph must contain its own stable entry`);\n'
+        + '  }',
+    }],
+  },
   {
     id: 'panel-imports-unversioned-card-entry',
     guard: 'node --test --test-name-pattern="#486 both stable entries" '