fix: terminal resize propagation and redraw

- Frontend: Add ResizeObserver with dimension tracking for accurate resize detection
- Frontend: Fix cleanup function to properly disconnect ResizeObserver
- Frontend: Use CSS grid for terminal wrapper layout
- Backend: Add duplicate dimension check to avoid unnecessary resizes
- Backend: Ensure stty command is sent correctly to container shell

apps/api/src/services/terminal_session.py

@@ -142,6 +142,11 @@ class TerminalSession:
         if self._closed:
             logger.warning("Cannot resize: session is closed")
             return
+        
+        # Only resize if dimensions actually changed
+        if cols == self._cols and rows == self._rows:
+            return
+            
         self._cols = cols
         self._rows = rows
         logger.info(f"resize() called for session {self.session_id}: {cols}x{rows}")

apps/web/src/components/terminal.tsx

@@ -260,18 +260,29 @@ export const TerminalComponent: React.FC<TerminalProps> = ({
       ws.send(data);
     });
 
-    // Handle window resize with debounce - use rAF to ensure layout settled
+    // Handle container resize with ResizeObserver for accurate dimension tracking
     let resizeTimeout: ReturnType<typeof setTimeout>;
-    const handleResize = () => {
+    let lastWidth = 0;
+    let lastHeight = 0;
+    const resizeObserver = new ResizeObserver((entries) => {
+      const entry = entries[0];
+      if (!entry) return;
+      
+      const { width, height } = entry.contentRect;
+      // Only trigger if dimensions actually changed
+      if (width === lastWidth && height === lastHeight) return;
+      lastWidth = width;
+      lastHeight = height;
+      
       clearTimeout(resizeTimeout);
       resizeTimeout = setTimeout(() => {
         requestAnimationFrame(() => {
+          if (!container.isConnected) return;
           fitTerminal();
         });
-      }, 100);
-    };
-
-    window.addEventListener("resize", handleResize);
+      }, 50);
+    });
+    resizeObserver.observe(container);
 
     // Refit after mobile header auto-hides (3s delay + 0.3s transition)
     const headerHideTimeout = setTimeout(() => {
@@ -306,7 +317,7 @@ export const TerminalComponent: React.FC<TerminalProps> = ({
     return () => {
       clearTimeout(resizeTimeout);
       clearTimeout(headerHideTimeout);
-      window.removeEventListener("resize", handleResize);
+      resizeObserver.disconnect();
       document.removeEventListener("visibilitychange", handleVisibilityChange);
       if (ws) {
         ws.close();

apps/web/src/styles.css

@@ -2506,8 +2506,8 @@ a.nav-item,
 }
 
 .terminal-wrapper {
-  display: flex;
-  flex-direction: column;
+  display: grid;
+  grid-template-rows: auto 1fr;
   flex: 1;
   min-height: 0;
   border: 1px solid var(--border);
@@ -2592,22 +2592,19 @@ a.nav-item,
 }
 
 .terminal-container {
-  flex: 1;
-  min-height: 0;
-  padding: var(--space-2);
-  display: flex;
-  flex-direction: column;
-  overflow: hidden;
   position: relative;
   width: 100%;
   height: 100%;
+  padding: var(--space-2);
+  overflow: hidden;
 }
 
 .terminal-container .xterm {
-  flex: 1;
-  min-height: 0;
-  width: 100%;
-  height: 100%;
+  position: absolute;
+  top: 0;
+  left: 0;
+  right: 0;
+  bottom: 0;
 }
 
 .terminal-container canvas {