fix: address Copilot review round 10 — structural const match, deep-link constants

- selectBranchIndex compares a discriminator structurally: a `const` may be
  an object or array, and deep-link arguments arrive as freshly parsed
  instances that could never be reference-equal to the schema's own.
- New applySchemaConstants, applied by InspectorView AFTER the deep link's
  `appArgs` are spread over the seeded defaults. The form renders a pinned
  field read-only, so a link disagreeing with one would otherwise auto-open an
  App with a hidden value contradicting the shape on screen.

Signed-off-by: cliffhall <cliff@futurescale.com>

core/json/rootUnion.ts

@@ -605,7 +605,12 @@ export function selectBranchIndex<T extends RootUnionSchema>(
     const supplied = pinned.filter(([name]) => values[name] !== undefined);
     if (
       supplied.length > 0 &&
-      supplied.every(([name, constValue]) => values[name] === constValue)
+      // Structural, not reference: a `const` may be an object or an array, and
+      // deep-link arguments arrive as freshly parsed instances that could never
+      // be `===` the schema's own.
+      supplied.every(([name, constValue]) =>
+        sameValue(values[name], constValue),
+      )
     ) {
       matches.push(index);
     }