fix(terminal): prevent double session creation, restore sessions on reload

Three fixes for multi-session terminal bugs:

1. Race-condition double creation: The auto-create effect fired twice because
   loadSessions returned 0 while an earlier createSession was still in flight.
   Added hasAutoCreated guard ref to ensure only one auto-create happens.

2. Page reload spawns new sessions: After server restart, list_terminal_sessions
   filtered out DB-only sessions (no in-memory counterpart), so the frontend
   thought no sessions existed and auto-created new ones. Reverted the filter
   so DB rows are always returned. The WebSocket handler now restores the
   in-memory session from the DB row on demand when connecting.

3. No input after connection: The backend _read_loop would break on any send
   error, causing asyncio.wait to cancel the _write_loop. Made _read_loop
   retry up to 3 times before giving up, preventing transient send errors
   from killing input handling.

Quality gates: pytest (15/15 passed), tsc clean

apps/web/src/pages/terminal.tsx

@@ -26,6 +26,7 @@ export const TerminalPage: React.FC = () => {
 	const [isFullscreen, setIsFullscreen] = useState(false);
 	const terminalRefs = useRef<Record<string, React.RefObject<TerminalRef>>>({});
 	const headerAutoHide = useAutoHide({ timeout: 3000, enabled: isMobile });
+	const hasAutoCreated = useRef(false);
 
 	const {
 		sessions,
@@ -39,9 +40,16 @@ export const TerminalPage: React.FC = () => {
 		error,
 	} = useTerminalSessions(instanceId ?? "");
 
-	// Auto-create default session if none exist
+	// Auto-create default session if none exist (guard against double-fire)
 	useEffect(() => {
-		if (!loading && sessions.length === 0 && !error && instanceId) {
+		if (
+			!loading &&
+			sessions.length === 0 &&
+			!error &&
+			instanceId &&
+			!hasAutoCreated.current
+		) {
+			hasAutoCreated.current = true;
 			void createSession("Session 1");
 		}
 	}, [loading, sessions.length, error, instanceId, createSession]);
@@ -232,16 +240,13 @@ export const TerminalPage: React.FC = () => {
 					{sessions
 						.filter((session) => session.id === activeSessionId)
 						.map((session) => (
-							<div
-								key={session.id}
-								className="terminal-instance active"
-							>
+							<div key={session.id} className="terminal-instance active">
 								<TerminalComponent
-										ref={terminalRefs.current[session.id]}
-										instanceId={instanceId}
-										sessionId={session.id}
-										onClose={() => handleClose(session.id)}
-										isMobile={true}
+									ref={terminalRefs.current[session.id]}
+									instanceId={instanceId}
+									sessionId={session.id}
+									onClose={() => handleClose(session.id)}
+									isMobile={true}
 								/>
 							</div>
 						))}
@@ -291,10 +296,7 @@ export const TerminalPage: React.FC = () => {
 				{sessions
 					.filter((session) => session.id === activeSessionId)
 					.map((session) => (
-						<div
-							key={session.id}
-							className="terminal-instance active"
-						>
+						<div key={session.id} className="terminal-instance active">
 							<TerminalComponent
 								ref={terminalRefs.current[session.id]}
 								instanceId={instanceId}