a /plugins screen to install, enable, disable and uninstall

the management surface for what the last commit made possible. two panels either
side of a selection that lives in ?selected= and is read by both independently,
so neither can be telling the other something stale — rows are real Links, not
buttons holding the name in a closure.

the detail panel shows what the tree declared (api, schema, sidecar, web),
because "installed and nothing happened" is otherwise a mystery, and it names
what uninstall does NOT do: neither disable nor uninstall deletes anything the
plugin stored, and the screen says so rather than leaving someone to guess
whether a button destroys their data.

a directory whose manifest will not parse is listed with its error rather than
skipped. a malformed plugin that simply does not appear is indistinguishable
from one nobody wrote.

`outdated` is surfaced as an Update button: the version on disk moving after an
install is the normal state on a developer's machine, and it should be visible
rather than inferred.

the four mutations are written out rather than generated in a loop — useMutation
is a hook, and a hook called from inside a helper is a rules-of-hooks violation
even when the call order happens to be stable. caught before it shipped.

verified against a running server: the spa builds (19.8 MB bundle containing the
new screen), / serves 200, /api/plugins answers authenticated and 401s without a
token. full suite 719 pass, same 10 pre-existing failures. live server and
plugin_installs left untouched.

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

src/apps/officer-web/Screens/Dashboard/Plugins/defaultLayout.ts

@@ -0,0 +1,14 @@
+import type { LayoutNode } from 'officerdev';
+
+// List left, detail right — a master list with a live preview, which is why the selection is `?selected=`
+// rather than a `/plugins/:appName` route: linking rows to the detail route would make it the whole page
+// and destroy the side-by-side. See docs/navigation-audit.md.
+export const defaultLayout: LayoutNode = {
+  type: 'group',
+  id: 'plugins-root',
+  direction: 'horizontal',
+  children: [
+    { node: { type: 'panel', id: 'plugins-list', appType: 'plugins-list' }, size: 32 },
+    { node: { type: 'panel', id: 'plugin-detail', appType: 'plugin-detail' }, size: 68 },
+  ],
+};