refactor(electrobun): modularize stores + shared UI components

Stores:
- notifications-store.svelte.ts: owns notifications array (was inline in App)
- workspace-store.svelte.ts: extended with addProjectFromWizard, loadGroupsFromDb,
  loadProjectsFromDb, derived getters (totalCost, totalTokens, mountedGroupIds)

Shared UI components (ui/):
- SegmentedControl.svelte: replaces repeated .seg button groups
- SliderInput.svelte: labeled range slider with value display
- StatusDot.svelte: colored dot with pulse support
- IconButton.svelte: icon-only button with tooltip, 3 sizes
- Section.svelte: settings section wrapper with heading

App.svelte: script 390→221 lines (removed all inline CRUD, delegates to stores)
ProjectCard: uses StatusDot shared component
AgentSettings + OrchestrationSettings: use SegmentedControl, SliderInput, Section

ui-electrobun/src/mainview/notifications-store.svelte.ts

@@ -0,0 +1,49 @@
+/**
+ * Notifications store — owns notification list and toast integration.
+ *
+ * Extracted from App.svelte inline state (Phase 2).
+ */
+
+// ── Types ─────────────────────────────────────────────────────────────────
+
+export interface Notification {
+  id: number;
+  message: string;
+  type: 'success' | 'warning' | 'info' | 'error';
+  time: string;
+}
+
+// ── State ─────────────────────────────────────────────────────────────────
+
+let notifications = $state<Notification[]>([
+  { id: 1, message: 'Agent completed: wake scheduler implemented', type: 'success', time: '2m ago' },
+  { id: 2, message: 'Context pressure: 78% on agent-orchestrator', type: 'warning', time: '5m ago' },
+  { id: 3, message: 'PTY daemon connected', type: 'info', time: '12m ago' },
+]);
+
+let nextId = $state(100);
+
+// ── Public API ────────────────────────────────────────────────────────────
+
+export function getNotifications(): Notification[] {
+  return notifications;
+}
+
+export function getNotifCount(): number {
+  return notifications.length;
+}
+
+export function addNotification(message: string, type: Notification['type'] = 'info'): void {
+  const now = new Date();
+  const time = `${now.getHours()}:${String(now.getMinutes()).padStart(2, '0')}`;
+  const id = nextId++;
+  notifications = [{ id, message, type, time }, ...notifications].slice(0, 100);
+}
+
+export function removeNotification(id: number): void {
+  notifications = notifications.filter(n => n.id !== id);
+}
+
+export function clearAll(): void {
+  notifications = [];
+}