Fix terminal size on connect — send dimensions after handshake

Root cause: The PTY is allocated at 80x24 during the SSH handshake.
The frontend xterm.js fits correctly to the container (e.g. 120x35),
but term.onResize fires before the backend connection is ready, so the
ResizeSession call is silently rejected. When the connection completes,
fitAddon.fit() sees the terminal already has the right cols/rows and
does NOT fire another onResize event. The PTY stays at 80x24.

Fix: On 'session:state → connected', explicitly read the current
terminal cols/rows and send them to the backend via ResizeSession,
bypassing the onResize event dependency.

Also fix empty-state ordering in addTab() — hide the empty-state
BEFORE activating the panel so the panel-container gets the full
workspace height immediately (empty-state has flex:1 and was stealing
half the height during initial layout).

Simplify createTerminal() fit logic — force a synchronous reflow
via offsetHeight access, then fit immediately.

frontend/src/js/terminal.js

@@ -67,23 +67,15 @@ class TerminalManager {
         const container = document.getElementById(containerId);
         term.open(container);
 
-        // Fit the terminal once the container has real dimensions.
-        // The panel may have just transitioned from display:none, so we
-        // poll until the container reports a non-trivial size.
+        // Force a synchronous layout reflow so the container reports its
+        // true dimensions, then fit the terminal to fill the space.
+        // eslint-disable-next-line no-unused-expressions
+        container.offsetHeight;
         const doFit = () => { try { fitAddon.fit(); } catch (_) { /* noop */ } };
-        let fitAttempts = 0;
-        const tryFit = () => {
-            fitAttempts++;
-            const rect = container.getBoundingClientRect();
-            if (rect.width > 10 && rect.height > 10) {
-                doFit();
-            } else if (fitAttempts < 20) {
-                // Container still has no size — retry
-                setTimeout(tryFit, 50);
-                return;
-            }
-        };
-        requestAnimationFrame(tryFit);
+        doFit();
+        // Belt-and-braces: retry once after a paint in case the initial
+        // reflow dimensions were still stale.
+        requestAnimationFrame(doFit);
 
         // Forward user keystrokes to the backend
         term.onData((data) => {