fix(terminal): keep the terminal resize observer alive across SSE init

initTerminal() creates the ResizeObserver on #terminalContainer once per page,
and _resetAllAppState() (run by handleInit on EVERY SSE init, page load
included) disconnected and dropped it. From the first init on, only a window
resize refit the terminal, so anything that resized just the terminal box left
xterm at its old row count with the bottom rows clipped behind the toolbar.

Pre-existing since the March app.js module split, but this release makes it
constant: #538's state rows grow and shrink the header whenever a session
starts or stops working, and #544 reserves lineage room when the first child
appears. Measured on the beta: header 115 -> 170 px, container 743 -> 688 px,
xterm stayed at 35 rows (32 fit) until a tab switch. initTerminal() already
disconnects any previous observer before creating one, so the reset has
nothing to clean up.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/web/public/app.js

@@ -4570,11 +4570,15 @@ class CodemanApp {
       }
       this.notificationManager.groupingMap.clear();
     }
-    // Disconnect terminal resize observer (prevents memory leak on reconnect)
-    if (this.terminalResizeObserver) {
-      this.terminalResizeObserver.disconnect();
-      this.terminalResizeObserver = null;
-    }
+    // ⚠️ The terminal resize observer is NOT reset here. initTerminal() owns its
+    // lifecycle (it runs once per page and disconnects any previous observer
+    // before creating one), and this reset runs on EVERY SSE init, page load
+    // included. It used to disconnect the observer "to prevent a leak", which
+    // left the terminal with no observer from the first init on: only a WINDOW
+    // resize ever refit it, so anything that resized just the terminal box
+    // (state rows and lineage room appearing in the header, the tab strip
+    // wrapping) clipped xterm's bottom rows behind the toolbar until a tab
+    // switch or a window resize.
     // Clear any other orphaned timers
     if (this.planLoadingTimer) {
       clearInterval(this.planLoadingTimer);