feat(web/ui): unify session opening and add repo card in project list

- Add openSession utility with tab deduplication/focus
- Use openSession in navbar live sessions, use-instance-actions, and project tool links
- Pass onAddRepository to ProjectListItem and add dashed 'Add Repository' card
- Style add-repo card in projects.css

apps/web/src/components/app-shell.tsx

@@ -2,6 +2,7 @@ import { Link, NavLink, Outlet, useLocation } from "react-router-dom";
 
 import type { Session } from "../api/sessions";
 import { useTheme } from "../hooks/use-theme";
+import { openSession } from "../utils/open-session";
 import { useAuth } from "../state/auth";
 import { useSessions } from "../state/sessions";
 import { useMobileViewport } from "../hooks/use-mobile-viewport";
@@ -33,19 +34,6 @@ const NAV_ITEMS: {
 const SessionItem = ({ session }: { session: Session }) => {
 	const isRunning = session.status === "running";
 
-	// Determine the link target:
-	// - Web tools open their tunnel URL
-	// - Terminal tools open the terminal page
-	// - Everything else falls back to the project page
-	const hasTerminal = session.tool_type_interfaces.includes("terminal");
-	const hasWeb = session.tool_type_interfaces.includes("web");
-	const href =
-		session.url && hasWeb
-			? session.url
-			: hasTerminal
-				? `/instances/${session.id}/terminal`
-				: `/projects/${session.project_id}`;
-
 	const contextName = session.workspace_name || session.repository_name;
 	const tooltipParts = [
 		session.display_name,
@@ -56,10 +44,9 @@ const SessionItem = ({ session }: { session: Session }) => {
 	tooltipParts.push(`(${session.status})`);
 
 	return (
-		<a
-			href={href}
-			target={`session-${session.id}`}
-			rel="noreferrer"
+		<button
+			type="button"
+			onClick={() => openSession(session)}
 			className="nav-item session-item"
 			title={tooltipParts.join(" · ")}
 		>
@@ -76,7 +63,7 @@ const SessionItem = ({ session }: { session: Session }) => {
 					{session.tool_type_name} · {session.project_name}
 				</span>
 			</span>
-		</a>
+		</button>
 	);
 };