fix(kit): what installing the template into a real core showed

The template was built into a running core - MariaDB, the real loader, a browser
- and both halves of the walk passed: core reconciled two Teams out of the
provider on the first boot, /public/teams/<slug>/members came back with
projected:true, and the clan page rendered core's activity feed and forum in the
two slots this module declared. That last one is the whole point of the phase: a
module whose id is not "uo" now gets core's Team content, which is what
website#160 fixed. module-uo's own guild page was walked on the same core and is
unchanged.

Two things the walk found, both of the kind only a browser can:

PageHeader takes `lead`, not `subtitle`. The template has been passing subtitle
since it was written, and an unknown prop on a React component is silently
dropped - so every page built from this template rendered its heading with
nothing under it, on a site where every core page has a line there. Nothing warns
anywhere. Fixed on all three pages, and chapter 2 now says to check prop names
against 3.4 rather than guessing them, beside the paragraph about `shell` that
exists for exactly the same reason.

"1 members" on the clan list.

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

template/client/src/routes/public/Clan.jsx

@@ -47,7 +47,7 @@ export default function Clan() {
         <>
           <PageHeader
             title={data.name}
-            subtitle={`${data.memberCount} members${data.abbr ? ` · ${data.abbr}` : ''}`}
+            lead={`${data.memberCount} members${data.abbr ? ` · ${data.abbr}` : ''}`}
           />
 
           {/* Core's per-Team notification control lands here — ABOVE the roster,