fix(chat): + menu opens downward when the prompt box sits too near the top

On the workspace home the box is high on the screen, so the menu and its
submenus (Project files) opened upward and were clipped off the top.
Measure the room above/below (viewport narrowed by clipping ancestors) at
open and drop the menu below the button, submenus top-aligned, when it fits better.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

client/src/components/run/ChatAddMenu.tsx

@@ -13,7 +13,8 @@
  * puts `/<name>` (`/<plugin>:<name>`) at the front of the message — the same
  * text the `/` autocomplete inserts, so the CLI runs it as typed. Both lists
  * are read when the menu first opens (`GET /api/cc-config/skills|plugins`),
- * and Manage opens the Claude config page on that tab.
+ * and Manage opens the Claude config page on that tab. The menu opens
+ * downward when the box sits too near the top to fit it above.
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
 
@@ -78,6 +79,35 @@ function loadLists(cwd: string): Promise<Lists> {
 
 const PANEL =
   "absolute w-60 rounded-xl border border-border bg-surface-1 py-1 shadow-lg animate-fade-in";
+/** Room the menu and its tallest submenu (Project files: search + list) need. */
+const MENU_ROOM = 380;
+
+/** The visible band the button sits in: the viewport, narrowed by any
+ * scrolling/clipping ancestor (the page body scrolls inside the layout). */
+function clipBand(el: HTMLElement): { top: number; bottom: number } {
+  let top = 0;
+  let bottom = window.innerHeight;
+  for (let p = el.parentElement; p; p = p.parentElement) {
+    const o = getComputedStyle(p);
+    if (/(auto|scroll|hidden|clip)/.test(o.overflowY + o.overflow)) {
+      const r = p.getBoundingClientRect();
+      top = Math.max(top, r.top);
+      bottom = Math.min(bottom, r.bottom);
+    }
+  }
+  return { top, bottom };
+}
+
+/** Open downward when there is not room above but more below. */
+function opensDown(el: HTMLElement | null): boolean {
+  if (!el) return false;
+  const r = el.getBoundingClientRect();
+  const band = clipBand(el);
+  const above = r.top - band.top;
+  const below = band.bottom - r.bottom;
+  return above < MENU_ROOM && below > above;
+}
+
 const ROW =
   "flex w-full items-center gap-2.5 px-3 py-1.5 text-left text-sm text-fg-secondary hover:bg-surface-3 hover:text-fg-primary";
 
@@ -195,6 +225,7 @@ export function ChatAddMenu({
   const { t } = useTranslation("run");
   const navigate = useNavigate();
   const [open, setOpen] = useState(false);
+  const [down, setDown] = useState(false);
   const [sub, setSub] = useState<Sub | null>(null);
   const [context, setContext] = useState<Attachment[] | null>(null);
   const [recent, setRecent] = useState<Attachment[]>([]);
@@ -286,6 +317,8 @@ export function ChatAddMenu({
         />
       ))
     );
+  // A submenu lines up with the menu's edge nearest the button.
+  const edge = down ? "top-0" : "bottom-0";
   const shownPlugin = lists?.plugins.find((p) => p.name === plugin);
 
   return (
@@ -296,13 +329,17 @@ export function ChatAddMenu({
         aria-label={t("chat.add")}
         title={t("chat.add")}
         aria-expanded={open}
-        onClick={() => (open ? close() : setOpen(true))}
+        onClick={() => {
+          if (open) return close();
+          setDown(opensDown(ref.current));
+          setOpen(true);
+        }}
         className="flex h-8 w-8 items-center justify-center rounded-full text-fg-muted transition-colors hover:bg-surface-3 hover:text-fg-primary"
       >
         <Plus className="h-4 w-4" />
       </button>
       {open && (
-        <div role="menu" data-testid="chat-add-menu" className={`${PANEL} bottom-full left-0 mb-2`}>
+        <div role="menu" data-testid="chat-add-menu" className={`${PANEL} left-0 ${down ? "top-full mt-2" : "bottom-full mb-2"}`}>
           <Row
             icon={<Paperclip className="h-4 w-4" />}
             label={t("chat.upload")}
@@ -376,13 +413,13 @@ export function ChatAddMenu({
           )}
 
           {sub === "project" && (
-            <div role="menu" className={`${PANEL} bottom-0 left-full ml-1 w-72 pt-2`}>
+            <div role="menu" className={`${PANEL} ${edge} left-full ml-1 w-72 pt-2`}>
               <ProjectFiles cwd={cwd} onPick={(rel) => attach(projectAttachment(rel))} />
             </div>
           )}
 
           {(sub === "context" || sub === "recent") && (
-            <div role="menu" className={`${PANEL} bottom-0 left-full ml-1`}>
+            <div role="menu" className={`${PANEL} ${edge} left-full ml-1`}>
               <div className="max-h-72 overflow-y-auto">
                 {(sub === "context" ? context : recent)?.length ? (
                   (sub === "context" ? context! : recent).map((it) => (
@@ -405,7 +442,7 @@ export function ChatAddMenu({
           )}
 
           {sub === "skills" && (
-            <div role="menu" className={`${PANEL} bottom-0 left-full ml-1`}>
+            <div role="menu" className={`${PANEL} ${edge} left-full ml-1`}>
               <div className="max-h-72 overflow-y-auto">{entries(lists?.skills ?? [], "")}</div>
               <div className="my-1 border-t border-border" />
               <Row
@@ -417,7 +454,7 @@ export function ChatAddMenu({
           )}
 
           {sub === "plugins" && (
-            <div role="menu" className={`${PANEL} bottom-0 left-full ml-1`}>
+            <div role="menu" className={`${PANEL} ${edge} left-full ml-1`}>
               <div className="max-h-72 overflow-y-auto">
                 {lists && lists.plugins.length === 0 && (
                   <p className="px-3 py-1.5 text-xs text-fg-muted">{t("chat.none")}</p>
@@ -443,7 +480,7 @@ export function ChatAddMenu({
                 onClick={() => manage("plugins")}
               />
               {shownPlugin && (
-                <div role="menu" className={`${PANEL} bottom-0 left-full ml-1`}>
+                <div role="menu" className={`${PANEL} ${edge} left-full ml-1`}>
                   <div className="max-h-72 overflow-y-auto">
                     {entries(
                       shownPlugin.items,