fix: address Copilot review round 37 — stale constants, inherited answers, prefixed labels

- The seeding effect re-applies constants as well as filling absences: an
  in-place schema change can move a `const` the user cannot edit, and the
  read-only field then displayed the new value while `values` still held the
  old one — which is what would be submitted. Ordinary defaults are still only
  ever added, so an edited field keeps what the user put there.
- hasMissingIn checks own-property presence: a required argument legally named
  `constructor` resolved to the inherited one and read as supplied, enabling
  a submit the schema rejects.
- The TUI keeps the declared name as a branch field's fallback title. The
  prefix is an internal field NAME, and buildFields labels from its map key —
  so the showcase displayed `__b0__address` where the schema says
  `address`.

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

clients/web/src/utils/jsonUtils.ts

@@ -352,6 +352,10 @@ function hasMissingIn(
   const required = Array.isArray(schema.required) ? schema.required : [];
   const properties = schema.properties ?? {};
   return required.some((field) => {
+    // `hasOwn` first: an argument legally named `constructor` would otherwise
+    // resolve to the inherited one and read as supplied, enabling a submit the
+    // schema rejects.
+    if (!Object.hasOwn(values, field)) return true;
     const value = values[field];
     if (value === null) {
       const fieldSchema = properties[field];