feat(electrobun): wire EVERYTHING — all settings persist, theme editor, marketplace

All settings wired to SQLite persistence:
- AgentSettings: shell, CWD, permissions, providers (JSON blob)
- SecuritySettings: branch policies (JSON array)
- ProjectSettings: per-project via setProject RPC
- OrchestrationSettings: wake, anchors, notifications
- AdvancedSettings: logging, OTLP, plugins, import/export JSON

Theme Editor:
- 26 color pickers (14 Accents + 12 Neutrals)
- Live CSS var preview as you pick colors
- Save custom theme to SQLite, cancel reverts
- Import/export theme as JSON
- Custom themes in dropdown with delete button

Extensions Marketplace:
- 8-plugin demo catalog (Browse/Installed tabs)
- Search/filter by name or tag
- Install/uninstall with SQLite persistence
- Plugin cards with emoji icons, tags, version

Terminal font hot-swap:
- fontStore.onTermFontChange() → xterm.js options update + fitAddon.fit()
- Resize notification to PTY daemon after font change

All 7 settings categories functional. Every control persists and takes effect.

ui-electrobun/src/mainview/SettingsDrawer.svelte

@@ -5,6 +5,7 @@
   import ProjectSettings       from './settings/ProjectSettings.svelte';
   import OrchestrationSettings from './settings/OrchestrationSettings.svelte';
   import AdvancedSettings      from './settings/AdvancedSettings.svelte';
+  import MarketplaceTab        from './settings/MarketplaceTab.svelte';
 
   interface Props {
     open: boolean;
@@ -13,7 +14,7 @@
 
   let { open, onClose }: Props = $props();
 
-  type CategoryId = 'appearance' | 'agents' | 'security' | 'projects' | 'orchestration' | 'advanced';
+  type CategoryId = 'appearance' | 'agents' | 'security' | 'projects' | 'orchestration' | 'advanced' | 'marketplace';
 
   interface Category {
     id: CategoryId;
@@ -28,6 +29,7 @@
     { id: 'projects',      label: 'Projects',      icon: '📁' },
     { id: 'orchestration', label: 'Orchestration', icon: '⚙' },
     { id: 'advanced',      label: 'Advanced',      icon: '🔧' },
+    { id: 'marketplace',   label: 'Marketplace',   icon: '🛒' },
   ];
 
   let activeCategory = $state<CategoryId>('appearance');
@@ -92,6 +94,8 @@
             <OrchestrationSettings />
           {:else if activeCategory === 'advanced'}
             <AdvancedSettings />
+          {:else if activeCategory === 'marketplace'}
+            <MarketplaceTab />
           {/if}
         </div>
       </div>
@@ -126,7 +130,6 @@
     to   { transform: translateX(0);    opacity: 1; }
   }
 
-  /* Header */
   .drawer-header {
     height: 3rem;
     display: flex;
@@ -164,7 +167,6 @@
     color: var(--ctp-text);
   }
 
-  /* Body: two-column layout */
   .drawer-body {
     flex: 1;
     min-height: 0;
@@ -172,7 +174,6 @@
     overflow: hidden;
   }
 
-  /* Category nav sidebar */
   .cat-nav {
     width: 8.5rem;
     flex-shrink: 0;
@@ -226,7 +227,6 @@
     text-overflow: ellipsis;
   }
 
-  /* Content area */
   .cat-content {
     flex: 1;
     min-width: 0;