fix: terminal shift-left bug and session sidebar naming/filtering

- Guard ResizeObserver in terminal against internal xterm DOM changes
  by tracking last width/height and only calling fit() on real resize
- Remove padding from .terminal-container and conflicting .xterm height
  override that caused measurement mismatches with xterm-addon-fit
- Filter live session sidebar to active statuses only (running, building,
  pending) instead of showing all sessions including stopped ones
- Add display name fallback across sidebar, sessions page, and instance
  list to prevent blank names when display_name is empty

Quality gates: tsc (pass), eslint (pass)

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

@@ -16,8 +16,11 @@ const NAV_ITEMS: { to: string; label: string; icon: IconName }[] = [
   { to: "/settings", label: "Settings", icon: "settings" }
 ];
 
+const ACTIVE_STATUSES = ["running", "building", "pending"];
+
 const SessionItem = ({ session }: { session: Session }) => {
   const isRunning = session.status === "running";
+  const displayName = session.display_name || session.tool_type_name || "Unnamed Session";
 
   return (
     <a
@@ -25,11 +28,11 @@ const SessionItem = ({ session }: { session: Session }) => {
       target={session.url ? "_blank" : undefined}
       rel={session.url ? "noopener noreferrer" : undefined}
       className="nav-item session-item"
-      title={`${session.display_name} (${session.status})`}
+      title={`${displayName} (${session.status})`}
     >
       <span className={`session-status ${isRunning ? "running" : ""}`} />
       <Icon name={session.tool_icon as IconName} size="sm" />
-      <span className="session-name">{session.display_name}</span>
+      <span className="session-name">{displayName}</span>
     </a>
   );
 };
@@ -101,13 +104,15 @@ export const AppShell = () => {
             );
           })}
           
-          {sessions.length > 0 && (
+          {sessions.filter((s) => ACTIVE_STATUSES.includes(s.status)).length > 0 && (
             <>
               <div className="nav-divider" />
               <div className="nav-section-title">Live sessions</div>
-              {sessions.map((session) => (
-                <SessionItem key={session.id} session={session} />
-              ))}
+              {sessions
+                .filter((s) => ACTIVE_STATUSES.includes(s.status))
+                .map((session) => (
+                  <SessionItem key={session.id} session={session} />
+                ))}
             </>
           )}
         </aside>

apps/web/src/components/instance-list.tsx

@@ -194,7 +194,7 @@ export const InstanceList = ({ projectId, repoId, toolTypes }: InstanceListProps
           {instances.map((instance) => (
             <div key={instance.id} className="instance-card">
               <div className="instance-info">
-                <div className="instance-name">{instance.display_name}</div>
+                <div className="instance-name">{instance.display_name || instance.tool_type_name || "Unnamed Instance"}</div>
                 <div className="instance-meta">
                   <span
                     className="status-dot"

apps/web/src/components/terminal.tsx

@@ -178,12 +178,26 @@ export const TerminalComponent: React.FC<TerminalProps> = ({
 
 		// Resize observer for container-level resize detection
 		let resizeTimeout: ReturnType<typeof setTimeout> | null = null;
-		const resizeObserver = new ResizeObserver(() => {
+		let lastWidth = 0;
+		let lastHeight = 0;
+		const resizeObserver = new ResizeObserver((entries) => {
 			if (resizeTimeout) {
 				clearTimeout(resizeTimeout);
 			}
+			const entry = entries[0];
+			if (!entry) return;
+			const { width, height } = entry.contentRect;
 			resizeTimeout = setTimeout(() => {
 				resizeTimeout = null;
+				// Guard against internal xterm DOM changes that don't affect container size
+				if (
+					Math.abs(width - lastWidth) < 1 &&
+					Math.abs(height - lastHeight) < 1
+				) {
+					return;
+				}
+				lastWidth = width;
+				lastHeight = height;
 				const prevCols = term.cols;
 				const prevRows = term.rows;
 				fitAddon.fit();

apps/web/src/pages/sessions.tsx

@@ -266,7 +266,7 @@ export const SessionsPage = () => {
               <h2>Last Session</h2>
               <div className="card last-session-card">
                 <div className="last-session-info">
-                  <h3>{lastSession.display_name}</h3>
+                  <h3>{lastSession.display_name || lastSession.tool_type_name || "Unnamed Session"}</h3>
                   <p className="muted">
                     {lastSession.tool_type_name} · {lastSession.project_name} · {lastSession.repository_name}
                   </p>
@@ -316,7 +316,7 @@ export const SessionsPage = () => {
                 {activeSessions.map((session) => (
                   <div className="card session-card" key={session.id}>
                     <div className="session-info">
-                      <h4>{session.display_name}</h4>
+                      <h4>{session.display_name || session.tool_type_name || "Unnamed Session"}</h4>
                       <p className="muted">
                         {session.tool_type_name} · {session.project_name}
                       </p>
@@ -445,7 +445,7 @@ export const SessionsPage = () => {
                 {recentSessions.map((session) => (
                   <div className="recent-session-item" key={session.id}>
                     <div className="recent-session-info">
-                      <span className="recent-session-name">{session.display_name}</span>
+                      <span className="recent-session-name">{session.display_name || session.tool_type_name || "Unnamed Session"}</span>
                       <span className="muted">
                         {session.tool_type_name} · {session.project_name}
                       </span>

apps/web/src/styles.css

@@ -2748,11 +2748,6 @@ a.nav-item,
 .terminal-container {
   flex: 1;
   min-height: 0;
-  padding: 0.25rem;
-}
-
-.terminal-container .xterm {
-  height: 100%;
 }
 
 .terminal-container .xterm-viewport {