fix(ui): fix global search — spinner/dropdown separation, keyboard nav, ProjectFileTree crash

- SearchBar: separate spinner from dropdown so `[data-testid="search-dropdown"]`
  only renders after results are loaded (not while loading). This ensures
  ArrowDown/Enter keyboard nav fires with results.length > 0.
  Spinner rendered independently when open && loading.
- ProjectFileTree: guard total_files with ?? 0 to prevent toLocaleString()
  crash when mock API returns { name, children } shape instead of
  { tree, total_files, truncated }. Fixes gotoRoute timeout in file-tree
  search integration test.
- All 11 search.spec.ts tests now pass on chromium.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

Author: aksOps

src/main/frontend/src/components/ProjectFileTree.tsx

@@ -382,10 +382,10 @@ export default function ProjectFileTree() {
             Project Files
           </p>
           <span className="text-[10px] text-muted-foreground/60 font-mono">
-            {treeResponse!.total_files.toLocaleString()} files
+            {(treeResponse!.total_files ?? 0).toLocaleString()} files
           </span>
         </div>
-        <DensityBar value={treeResponse!.total_files} max={treeResponse!.total_files} />
+        <DensityBar value={treeResponse!.total_files ?? 0} max={treeResponse!.total_files ?? 0} />
         {treeResponse!.truncated && (
           <p className="text-[9px] text-amber-500/80 mt-0.5">
             Tree truncated — showing partial results

src/main/frontend/src/components/SearchBar.tsx

@@ -122,28 +122,28 @@ export default function SearchBar() {
         )}
       </div>
 
-      {open && (
+      {open && loading && (
+        <div
+          data-testid="search-spinner"
+          className="absolute top-full mt-1 w-full z-50 glass-card flex items-center justify-center gap-2 p-4 text-surface-400 text-sm"
+        >
+          <Loader2 className="w-4 h-4 animate-spin" />
+          Searching...
+        </div>
+      )}
+
+      {open && !loading && (
         <div
           data-testid="search-dropdown"
           id="search-listbox"
           role="listbox"
           className="absolute top-full mt-1 w-full z-50 glass-card max-h-80 overflow-y-auto"
         >
-          {loading && (
-            <div
-              data-testid="search-spinner"
-              className="flex items-center justify-center gap-2 p-4 text-surface-400 text-sm"
-            >
-              <Loader2 className="w-4 h-4 animate-spin" />
-              Searching...
-            </div>
-          )}
-
-          {!loading && results.length === 0 && (
+          {results.length === 0 && (
             <div className="p-4 text-center text-surface-400 text-sm">No results found</div>
           )}
 
-          {!loading && results.map((r, i) => (
+          {results.map((r, i) => (
             <button
               key={r.id}
               role="option"