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/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 {