feat(electrobun): groups, cloning, shortcuts, custom window — all 5 features

Groups Sidebar:
- SQLite groups table (4 seeded: Development, Testing, DevOps, Research)
- Left icon rail with emoji group icons, Ctrl+1-4 switching
- Active group highlighted, projects filtered by group

Project Cloning:
- Clone button on project cards (fork icon)
- git worktree add via Bun.spawn (array form, no shell strings)
- 3-clone limit, branch name validation, pending-status pattern
- Clone cards: WT badge + branch name + accent top border
- Chain link SVG icons between linked clones in grid

Keyboard Shortcuts:
- keybinding-store.svelte.ts: 16 defaults across 4 categories
- Two-scope: document capture + terminal focus guard
- KeyboardSettings.svelte: search, click-to-capture, conflict detection
- Per-binding reset + Reset All

Custom Window:
- titleBarStyle: "hidden" — no native title bar
- Vertical "AGOR" text in left sidebar (writing-mode: vertical-rl)
- Floating window controls badge (minimize/maximize/close)
- Draggable region via -webkit-app-region: drag
- Window frame persisted to SQLite (debounced 500ms)

Window is resizable by default (Electrobun BrowserWindow).

ui-electrobun/src/mainview/SettingsDrawer.svelte

@@ -6,6 +6,7 @@
   import OrchestrationSettings from './settings/OrchestrationSettings.svelte';
   import AdvancedSettings      from './settings/AdvancedSettings.svelte';
   import MarketplaceTab        from './settings/MarketplaceTab.svelte';
+  import KeyboardSettings      from './settings/KeyboardSettings.svelte';
 
   interface Props {
     open: boolean;
@@ -14,7 +15,7 @@
 
   let { open, onClose }: Props = $props();
 
-  type CategoryId = 'appearance' | 'agents' | 'security' | 'projects' | 'orchestration' | 'advanced' | 'marketplace';
+  type CategoryId = 'appearance' | 'agents' | 'security' | 'projects' | 'orchestration' | 'advanced' | 'marketplace' | 'keyboard';
 
   interface Category {
     id: CategoryId;
@@ -28,6 +29,7 @@
     { id: 'security',      label: 'Security',      icon: '🔒' },
     { id: 'projects',      label: 'Projects',      icon: '📁' },
     { id: 'orchestration', label: 'Orchestration', icon: '⚙' },
+    { id: 'keyboard',      label: 'Keyboard',      icon: '⌨' },
     { id: 'advanced',      label: 'Advanced',      icon: '🔧' },
     { id: 'marketplace',   label: 'Marketplace',   icon: '🛒' },
   ];
@@ -94,6 +96,8 @@
             <OrchestrationSettings />
           {:else if activeCategory === 'advanced'}
             <AdvancedSettings />
+          {:else if activeCategory === 'keyboard'}
+            <KeyboardSettings />
           {:else if activeCategory === 'marketplace'}
             <MarketplaceTab />
           {/if}