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`outdated` is surfaced as an Update button: the version on disk moving after an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/Layout/Dock.tsx

@@ -149,6 +149,7 @@ import {
   Clapperboard,
   GitBranch,
   Store,
+  Puzzle,
 } from 'lucide-react';
 
 /**
@@ -181,6 +182,8 @@ export const CORE_DOCK_ITEMS: DockItem[] = [
   // Core by necessity: the store is how every other feature arrives, so it can never be one of the
   // things that disappears when uninstalled.
   { label: 'App store', to: '/app-store', icon: Store, color: '#64748b' },
+  // Core, not contributed by a plugin: this is the screen that installs them, so it cannot arrive with one.
+  { label: 'Plugins', to: '/plugins', icon: Puzzle, color: '#94a3b8' },
 ];
 
 /**