every plugin route renders a workspace, and it is not a rule you can forget

an exclusionary rule, made structural. a plugin does not render a screen: it
contributes panels and says how they are arranged, and the shell renders
WorkspaceView around them.

    web/panels.ts   appRegistryMetas — at least one panel
    web/layout.ts   defaultLayout — how they are arranged

both required the moment web/ exists, and missing either is refused at discovery
by name and with the reason. tested:

    probeplug: has a web/ directory but is missing web/layout.ts.
    Every plugin route renders a Workspace: contribute panels and a layout,
    not a screen.

there is deliberately no way to export a component. one that could would be free
to render a bare div, a full-page form, or its own navigation, and the platform
would become a shell hosting strangers' layouts rather than one application.
non-compliance is not so much refused as unrepresentable — there is nowhere to
put a screen.

the shell registers <prefix> and <prefix>/:section, exactly as the core screens
do, so a plugin's sections stay addressable and cmd-clickable, and panels read
useParams independently rather than passing state between themselves.
appTypes.allowed is pinned to that plugin's own keys, so a persisted layout
naming something else falls back instead of rendering another plugin's panel
inside this screen.

the example plugin is rebuilt to model it — two panels, a layout, one of them
calling its own /api/example/ping through useClient — because the reference
implementation is what everyone copies.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

plugins/example/web/ExampleDetail.tsx

@@ -0,0 +1,23 @@
+import { useParams } from 'react-router';
+
+// The second panel, reading the URL rather than being told by its sibling.
+//
+// The shell registers `<prefix>` and `<prefix>/:section`, so a plugin's sections are addressable,
+// linkable and cmd-clickable — the same convention every core screen follows. Panels read `useParams`
+// independently; nothing is passed between them, so they cannot disagree.
+export const ExampleDetail = () => {
+  const { section } = useParams();
+
+  return (
+    <div className="h-full overflow-auto p-6">
+      <h2 className="text-lg font-semibold text-duck-dark">Detail</h2>
+      <p className="mt-1 text-sm text-duck-dark/60">
+        Section from the URL: <code>{section ?? '(none)'}</code>
+      </p>
+      <p className="mt-3 text-xs text-duck-dark/40">
+        Try <code>/example/anything</code> — this panel reads it from <code>useParams</code>, with no state passed from
+        the panel beside it.
+      </p>
+    </div>
+  );
+};