fix(app): working scrollback search + stop prompt duplication on focus

Search fixes:
- TerminalView sets allowProposedApi (the search addon's match decorations
  use registerMarker/registerDecoration); without it findNext threw before
  firing results, so the counter was stuck at 0/0.
- The search bar now renders inside the panel it targets (in the header)
  instead of a global top-right overlay, so it's obvious which panel is
  searched.
- Search is anchored to the panel it was opened on (searchSurfaceId) and no
  longer follows focus — opening it in one panel and switching away no longer
  shows it open elsewhere.

Prompt duplication:
- The focus border was 1px when unfocused, 2px when focused; with border-box
  that resized the content on every focus switch, firing ResizeObserver -> fit
  -> PTY SIGWINCH and making zsh/powerlevel10k reprint its prompt. The border
  is now a constant 2px, color-only on focus.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/src/App.tsx

@@ -3,7 +3,6 @@ import { LayoutEngine } from "./LayoutEngine";
 import { Sidebar } from "./Sidebar";
 import { TopBar } from "./TopBar";
 import { CenterToolbar } from "./CenterToolbar";
-import { SearchBar } from "./SearchBar";
 import { Wizard } from "./Wizard";
 import { EventCenter } from "./EventCenter";
 import { maybeNotify } from "./notify";
@@ -35,9 +34,10 @@ export function App() {
   const [health, setHealth] = useState<DaemonHealth | null>(null);
   const [connected, setConnected] = useState(false);
   const [focusedId, setFocusedId] = useState<string | null>(null);
-  const [searchOpen, setSearchOpen] = useState(false);
+  const [searchSurfaceId, setSearchSurfaceId] = useState<string | null>(null);
   const [searchNonce, setSearchNonce] = useState(0);
   const activeRef = useRef<string | null>(null);
+  const effectiveFocusRef = useRef<string | null>(null);
   const wsRef = useRef<WorkspaceView[]>([]);
   activeRef.current = activeId;
   wsRef.current = workspaces;
@@ -107,7 +107,11 @@ export function App() {
   useEffect(() => {
     const onKey = (e: KeyboardEvent) => {
       if ((e.metaKey || e.ctrlKey) && e.key.toLowerCase() === "f") {
-        if (activeRef.current) { e.preventDefault(); setSearchOpen(true); setSearchNonce((n) => n + 1); }
+        if (activeRef.current && effectiveFocusRef.current) {
+          e.preventDefault();
+          setSearchSurfaceId(effectiveFocusRef.current); // anchor to the focused panel
+          setSearchNonce((n) => n + 1);
+        }
       }
     };
     window.addEventListener("keydown", onKey);
@@ -121,6 +125,7 @@ export function App() {
   const active = workspaces.find((w) => w.id === activeId) ?? null;
   const leaves = active ? leafIds(active.layout) : [];
   const effectiveFocus = focusedId && leaves.includes(focusedId) ? focusedId : leaves[0] ?? null;
+  effectiveFocusRef.current = effectiveFocus;
 
   function selectWorkspace(id: string) {
     setActiveId(id);
@@ -135,13 +140,12 @@ export function App() {
         {sidebarOpen && <Sidebar groups={groups} workspaces={workspaces} activeId={activeId} onSelect={selectWorkspace} onNew={() => setWizard(true)} health={health} connected={connected} />}
         <div style={{ flex: 1, display: "flex", flexDirection: "column", minWidth: 0 }}>
           {active && (
-            <CenterToolbar selected="" onSelect={(p) => { if (active) void applyPreset(active.id, p, []); }} onOpenSearch={() => setSearchOpen(true)} />
+            <CenterToolbar selected="" onSelect={(p) => { if (active) void applyPreset(active.id, p, []); }} onOpenSearch={() => { if (effectiveFocus) { setSearchSurfaceId(effectiveFocus); setSearchNonce((n) => n + 1); } }} />
           )}
           <div style={{ flex: 1, minHeight: 0, position: "relative" }}>
             {active
-              ? <LayoutEngine workspaceId={active.id} layout={active.layout} running={running} states={states} surfaces={active.surfaces} focusedId={effectiveFocus} onFocus={setFocusedId} zoomed={active.zoomed} />
+              ? <LayoutEngine workspaceId={active.id} layout={active.layout} running={running} states={states} surfaces={active.surfaces} focusedId={effectiveFocus} onFocus={setFocusedId} zoomed={active.zoomed} searchSurfaceId={searchSurfaceId} searchNonce={searchNonce} onCloseSearch={() => setSearchSurfaceId(null)} />
               : <div style={{ color: COLORS.textMuted, padding: 24 }}>No workspace — create one to begin.</div>}
-            {searchOpen && active && <SearchBar surfaceId={effectiveFocus} reopenNonce={searchNonce} onClose={() => setSearchOpen(false)} />}
           </div>
         </div>
         {eventsOpen && (