improve chat pane styling and layout

src/app.tsx

@@ -66,7 +66,7 @@ export function App() {
     let alive = true
     const poll = () => listSessions().then(s => { if (alive) setSessions(s) }).catch(() => {})
     poll()
-    const id = setInterval(poll, 5000)
+    const id = setInterval(poll, 250)
     return () => { alive = false; clearInterval(id) }
   }, [])
 
@@ -90,7 +90,7 @@ export function App() {
     }
 
     poll()
-    const id = setInterval(poll, 2000)
+    const id = setInterval(poll, 250)
     return () => { alive = false; clearInterval(id) }
   }, [selectedId])
 

src/components/ChatPane.tsx

@@ -120,12 +120,20 @@ export function ChatPane({ session, cfg, messages, onSend, onStop, browsePath, b
   const [atBottom, setAtBottom] = useState(true)
 
   const isRunning = !!cfg?.state && cfg.state !== 'idle' && cfg.state !== 'stopped'
+  const lastLen = messages.length > 0 ? messages[messages.length - 1].content.length : 0
 
   useEffect(() => {
     if (atBottom && listRef.current) {
       listRef.current.scrollTop = listRef.current.scrollHeight
     }
-  }, [messages.length, isRunning, atBottom])
+  }, [messages.length, lastLen, isRunning, atBottom])
+
+  const scrollToBottom = () => {
+    if (listRef.current) {
+      listRef.current.scrollTop = listRef.current.scrollHeight
+      setAtBottom(true)
+    }
+  }
 
   useEffect(() => {
     if (!listRef.current) return
@@ -264,6 +272,12 @@ export function ChatPane({ session, cfg, messages, onSend, onStop, browsePath, b
         )}
       </div>
 
+      {!atBottom && (
+        <button class="scroll-to-bottom" onClick={scrollToBottom} aria-label="Scroll to bottom">
+          ↓
+        </button>
+      )}
+
       <PromptBar running={isRunning} onSend={onSend} onStop={onStop} />
     </main>
   )

src/style.css

@@ -317,6 +317,7 @@ input, select, textarea { font-family: inherit; }
   overflow: hidden;
   height: 100%;
   background: var(--bg);
+  position: relative;
 }
 
 /* ---- Welcome ---- */
@@ -1075,3 +1076,29 @@ details[open] > .tool-header::before {
   font-style: italic;
   color: var(--text-faint);
 }
+
+/* ---- Scroll to bottom ---- */
+.scroll-to-bottom {
+  position: absolute;
+  bottom: 80px;
+  left: 50%;
+  transform: translateX(-50%);
+  width: 36px;
+  height: 36px;
+  border-radius: 50%;
+  border: 1px solid var(--border);
+  background: var(--bg-elevated);
+  color: var(--text-dim);
+  font-size: 18px;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  cursor: pointer;
+  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
+  z-index: 10;
+  transition: opacity 0.15s, border-color 0.15s;
+}
+.scroll-to-bottom:hover {
+  border-color: var(--accent);
+  color: var(--accent);
+}