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/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();