MAESTRO: Add unit tests for same file open in multiple sessions

Verify that the file tab system correctly allows the same file to be
open in multiple sessions simultaneously. Each session maintains its
own independent file tab state (scroll position, search query, edit
mode) even when viewing the same file path.

Tests added:
- allows the same file path to be open in different sessions simultaneously
- each session maintains independent state for the same file
- sessions can have different number of tabs for the same files

src/__tests__/renderer/contexts/SessionContext.test.tsx

@@ -548,6 +548,130 @@ describe('SessionContext - Session Switching with File Tabs', () => {
 		});
 	});
 
+	describe('same file in multiple sessions', () => {
+		it('allows the same file path to be open in different sessions simultaneously', () => {
+			// Both sessions have the SAME file path open
+			const sharedFilePath = '/shared/config.ts';
+
+			const session1 = makeSession({
+				id: 'session-1',
+				name: 'Session 1',
+				filePreviewTabs: [makeFilePreviewTab({
+					id: 's1-config',
+					path: sharedFilePath,
+					name: 'config',
+					content: 'session 1 content',
+					scrollTop: 100,
+				})],
+				activeFileTabId: 's1-config',
+			});
+			const session2 = makeSession({
+				id: 'session-2',
+				name: 'Session 2',
+				filePreviewTabs: [makeFilePreviewTab({
+					id: 's2-config',
+					path: sharedFilePath, // Same path
+					name: 'config',
+					content: 'session 2 content',
+					scrollTop: 500,
+				})],
+				activeFileTabId: 's2-config',
+			});
+
+			render(<TestAppWrapper initialSessions={[session1, session2]} initialActiveSessionId="session-1" />);
+
+			// Session 1 sees its own tab
+			expect(screen.getByTestId('file-path-s1-config')).toHaveTextContent(sharedFilePath);
+			expect(screen.getByTestId('file-scroll-s1-config')).toHaveTextContent('100');
+			// Session 2's tab not visible
+			expect(screen.queryByTestId('file-path-s2-config')).not.toBeInTheDocument();
+		});
+
+		it('each session maintains independent state for the same file', async () => {
+			const sharedFilePath = '/shared/utils.ts';
+
+			const session1 = makeSession({
+				id: 'session-1',
+				name: 'Session 1',
+				filePreviewTabs: [makeFilePreviewTab({
+					id: 's1-utils',
+					path: sharedFilePath,
+					scrollTop: 0,
+					searchQuery: 'function',
+					editMode: false,
+				})],
+				activeFileTabId: 's1-utils',
+			});
+			const session2 = makeSession({
+				id: 'session-2',
+				name: 'Session 2',
+				filePreviewTabs: [makeFilePreviewTab({
+					id: 's2-utils',
+					path: sharedFilePath, // Same file
+					scrollTop: 2000,
+					searchQuery: 'const',
+					editMode: true,
+				})],
+				activeFileTabId: 's2-utils',
+			});
+
+			render(<TestAppWrapper initialSessions={[session1, session2]} initialActiveSessionId="session-1" />);
+
+			// Session 1: scroll=0, search='function', not editing
+			expect(screen.getByTestId('file-scroll-s1-utils')).toHaveTextContent('0');
+			expect(screen.getByTestId('file-search-s1-utils')).toHaveTextContent('function');
+			expect(screen.getByTestId('file-edit-s1-utils')).toHaveTextContent('viewing');
+
+			// Switch to session 2
+			await act(async () => {
+				screen.getByTestId('switch-to-session-2').click();
+			});
+
+			// Session 2: scroll=2000, search='const', editing
+			expect(screen.getByTestId('file-scroll-s2-utils')).toHaveTextContent('2000');
+			expect(screen.getByTestId('file-search-s2-utils')).toHaveTextContent('const');
+			expect(screen.getByTestId('file-edit-s2-utils')).toHaveTextContent('editing');
+
+			// Switch back to session 1
+			await act(async () => {
+				screen.getByTestId('switch-to-session-1').click();
+			});
+
+			// Session 1's state is still intact
+			expect(screen.getByTestId('file-scroll-s1-utils')).toHaveTextContent('0');
+			expect(screen.getByTestId('file-search-s1-utils')).toHaveTextContent('function');
+			expect(screen.getByTestId('file-edit-s1-utils')).toHaveTextContent('viewing');
+		});
+
+		it('sessions can have different number of tabs for the same files', () => {
+			// Session 1 has 3 files open, session 2 has 2 of the same files
+			const session1 = makeSession({
+				id: 'session-1',
+				name: 'Session 1',
+				filePreviewTabs: [
+					makeFilePreviewTab({ id: 's1-a', path: '/shared/a.ts' }),
+					makeFilePreviewTab({ id: 's1-b', path: '/shared/b.ts' }),
+					makeFilePreviewTab({ id: 's1-c', path: '/shared/c.ts' }),
+				],
+				activeFileTabId: 's1-a',
+			});
+			const session2 = makeSession({
+				id: 'session-2',
+				name: 'Session 2',
+				filePreviewTabs: [
+					makeFilePreviewTab({ id: 's2-a', path: '/shared/a.ts' }),
+					makeFilePreviewTab({ id: 's2-c', path: '/shared/c.ts' }), // Same files, different count
+				],
+				activeFileTabId: 's2-c',
+			});
+
+			render(<TestAppWrapper initialSessions={[session1, session2]} initialActiveSessionId="session-1" />);
+
+			// Session 1 has 3 tabs
+			expect(screen.getByTestId('file-tabs-count')).toHaveTextContent('3');
+		});
+	});
+
 	describe('rapid session switching', () => {
 		it('handles rapid session switching without losing state', async () => {
 			const sessions = Array.from({ length: 5 }, (_, i) =>