Fix terminal not resizing when zoom button is clicked

Use ghostty-web's FitAddon to recalculate terminal cols/rows from the
container's pixel dimensions on resize. Previously, the ResizeObserver
only forwarded stale dimensions to the PTY backend. Now FitAddon.fit()
recomputes the correct grid size using font metrics before signaling
the PTY, so the shell adapts to the new window size.

Assisted-By: docker-agent

Author: dgageot

handlers/resources/terminal.html

@@ -16,7 +16,7 @@
         // Use ghostty-web terminal emulator.
         // PR #136 (https://github.com/coder/ghostty-web/pull/136) fixes wheel
         // events with mouse tracking for proper tmux/vim pane scrolling.
-        const { init, Terminal } = await import(
+        const { init, Terminal, FitAddon } = await import(
             'https://cdn.jsdelivr.net/npm/ghostty-web@0.4.0/dist/ghostty-web.js'
         );
 
@@ -36,6 +36,12 @@
 
         term.open(container);
 
+        // FitAddon recalculates terminal cols/rows from the container's
+        // pixel dimensions and calls term.resize(), which fires onResize.
+        const fitAddon = new FitAddon();
+        term.loadAddon(fitAddon);
+        fitAddon.fit();
+
         // Connect to the WebSocket PTY backend.
         const proto = location.protocol === 'https:' ? 'wss:' : 'ws:';
         const ws = new WebSocket(proto + '//' + location.host + '/ws/terminal' + location.search);
@@ -50,7 +56,8 @@
             // Send initial resize.
             sendResize();
 
-            // Handle terminal resize.
+            // Handle terminal resize: when FitAddon recalculates dimensions
+            // on container size changes, this forwards the new size to the PTY.
             term.onResize(sendResize);
         };
 
@@ -74,11 +81,12 @@
             }));
         }
 
-        // Resize terminal when the window resizes.
+        // Automatically refit terminal when the container resizes (e.g.
+        // when the fake-window zoom button is clicked). FitAddon.fit()
+        // recalculates cols/rows from the new container size, calls
+        // term.resize(), which fires onResize → sendResize → PTY resize.
         new ResizeObserver(() => {
-            if (ws.readyState === WebSocket.OPEN) {
-                sendResize();
-            }
+            fitAddon.fit();
         }).observe(container);
     </script>
 </body>