MAESTRO: Add unified tab system props to TabBar interface

- Add UnifiedTab discriminated union type to types/index.ts
- Add new props to TabBarProps: unifiedTabs, activeFileTabId,
  onFileTabSelect, onFileTabClose
- Props are optional for backwards compatibility during transition
- Phase 3 of file preview tabs implementation

src/renderer/components/TabBar.tsx

@@ -19,7 +19,7 @@ import {
 	ChevronsRight,
 	Loader2,
 } from 'lucide-react';
-import type { AITab, Theme } from '../types';
+import type { AITab, Theme, FilePreviewTab, UnifiedTab } from '../types';
 import { hasDraft } from '../utils/tabHelpers';
 
 interface TabBarProps {
@@ -60,6 +60,16 @@ interface TabBarProps {
 	onCloseTabsLeft?: () => void;
 	/** Handler to close tabs to the right of active tab */
 	onCloseTabsRight?: () => void;
+
+	// === Unified Tab System Props (Phase 3) ===
+	/** Merged ordered list of AI and file preview tabs for unified rendering */
+	unifiedTabs?: UnifiedTab[];
+	/** Currently active file tab ID (null if an AI tab is active) */
+	activeFileTabId?: string | null;
+	/** Handler to select a file preview tab */
+	onFileTabSelect?: (tabId: string) => void;
+	/** Handler to close a file preview tab */
+	onFileTabClose?: (tabId: string) => void;
 }
 
 interface TabProps {
@@ -924,6 +934,11 @@ function TabBarInner({
 	onCloseOtherTabs,
 	onCloseTabsLeft,
 	onCloseTabsRight,
+	// Unified tab system props (Phase 3)
+	unifiedTabs: _unifiedTabs,
+	activeFileTabId: _activeFileTabId,
+	onFileTabSelect: _onFileTabSelect,
+	onFileTabClose: _onFileTabClose,
 }: TabBarProps) {
 	const [draggingTabId, setDraggingTabId] = useState<string | null>(null);
 	const [dragOverTabId, setDragOverTabId] = useState<string | null>(null);

src/renderer/types/index.ts

@@ -465,6 +465,15 @@ export interface FilePreviewTab {
  */
 export type UnifiedTabRef = { type: 'ai' | 'file'; id: string };
 
+/**
+ * Unified tab entry for rendering in TabBar.
+ * Discriminated union that includes the full tab data for each type.
+ * Used by TabBar to render both AI and file tabs in a single list.
+ */
+export type UnifiedTab =
+	| { type: 'ai'; id: string; data: AITab }
+	| { type: 'file'; id: string; data: FilePreviewTab };
+
 export interface Session {
 	id: string;
 	groupId?: string;