refactor(electrobun): centralize all shared state into global stores

New stores:
- ui-store.svelte.ts: settingsOpen, paletteOpen, searchOpen, notifDrawerOpen,
  showWizard, settingsCategory, projectToDelete, showAddGroup, newGroupName
- project-tabs-store.svelte.ts: per-project activeTab + activatedTabs via Map

Wired:
- App.svelte: 8 inline $state removed, reads/writes via ui-store
- ProjectCard: activeTab/activatedTabs from project-tabs-store
- SettingsDrawer: activeCategory from ui-store
- CommandPalette: 4 commands call ui-store directly (no CustomEvent dispatch)

Components are now pure view layers reading from stores.

ui-electrobun/src/mainview/SettingsDrawer.svelte

@@ -10,6 +10,10 @@
   import RemoteMachinesSettings   from './settings/RemoteMachinesSettings.svelte';
   import DiagnosticsTab           from './settings/DiagnosticsTab.svelte';
   import { t } from './i18n.svelte.ts';
+  import {
+    getSettingsCategory, setSettingsCategory,
+    type SettingsCategory,
+  } from './ui-store.svelte.ts';
 
   interface Props {
     open: boolean;
@@ -18,7 +22,7 @@
 
   let { open, onClose }: Props = $props();
 
-  type CategoryId = 'appearance' | 'agents' | 'security' | 'projects' | 'orchestration' | 'machines' | 'advanced' | 'marketplace' | 'keyboard' | 'diagnostics';
+  type CategoryId = SettingsCategory;
 
   interface Category {
     id: CategoryId;
@@ -43,7 +47,7 @@
     CATEGORY_DEFS.map(d => ({ id: d.id, label: t(d.key as any), icon: d.icon }))
   );
 
-  let activeCategory = $state<CategoryId>('appearance');
+  let activeCategory = $derived(getSettingsCategory());
 
   function handleBackdropClick(e: MouseEvent) {
     if (e.target === e.currentTarget) onClose();
@@ -83,7 +87,7 @@
           <button
             class="cat-btn"
             class:active={activeCategory === cat.id}
-            onclick={() => activeCategory = cat.id}
+            onclick={() => setSettingsCategory(cat.id)}
             aria-current={activeCategory === cat.id ? 'page' : undefined}
           >
             <span class="cat-icon" aria-hidden="true">{cat.icon}</span>