fix(files): a workspace whose folder was deleted leaves the Files places

The lane payload carries folder_missing (ENOENT/ENOTDIR only). Files hides
such a workspace and never reopens it as the default place; the Workspace
sidebar strikes its name through with a hint to remove it from its menu.
A folder that cannot be read no longer keeps the previous folder's entries
under its error, and a change in Files re-reads the workspace list.

client/src/components/lanes/FileExplorer.tsx

@@ -369,16 +369,21 @@ export function FileBrowser({
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [laneId, initialHome, session, source, initialPath]);
 
-  useEffect(() => {
+  // Re-read after every change here too: deleting a workspace's folder takes
+  // it out of the places (a workspace whose folder is gone has nothing to show).
+  const loadLanes = useCallback(() => {
     api.lanes
       .list()
       .then((r) => setLanes(r.lanes))
       .catch(() => setLanes([]));
+  }, []);
+  useEffect(() => {
+    loadLanes();
     api.files
       .homes()
       .then((r) => setHomes(r.homes))
       .catch(() => setHomes([]));
-  }, []);
+  }, [loadLanes]);
   // Another user's home (an admin's view) is read-only.
   const ro = isHomePlace(target) && !!homes.find((h) => h.id === target.home)?.readOnly;
   // Clone into the open folder: the absolute path of a workspace's own folder
@@ -439,6 +444,8 @@ export function FileBrowser({
       } else if (view === "trash") setTrash((await api.files.trash(target)).items);
       else setListing(await api.files.list(target, path));
     } catch (e) {
+      // Never leave the last folder's entries under another folder's error.
+      if (view === "files") setListing(null);
       // A dashboard that does not know /fs yet (not restarted) answers 404.
       setError(
         (e as { status?: number }).status === 404 && !errCode(e) ? t("fx.unavailable") : errText(e)
@@ -455,6 +462,7 @@ export function FileBrowser({
 
   const changed = () => {
     void load();
+    loadLanes();
     onChanged?.();
   };
 
@@ -932,11 +940,18 @@ export function FileBrowser({
   // owner whose home this viewer may not open (an analyst's view of other
   // users) still gets a row, one that only groups. A workspace with no owner
   // stays in the flat Workspaces list. Which rows are open is per browser.
+  // A workspace whose folder was deleted has nothing to browse — it stays a
+  // place only while it is the one open (so its error has a row to sit on).
+  const placeLanes = useMemo(
+    () =>
+      lanes.filter((l) => !l.folder_missing || (!isHomePlace(target) && laneOf(target) === l.id)),
+    [lanes, target]
+  );
   const { lanesOfHome, userRows } = useMemo(() => {
     const ids = new Set(homes.map((h) => h.id));
     const map = new Map<string, Lane[]>();
     const extra = new Map<string, UserRow>();
-    for (const l of lanes) {
+    for (const l of placeLanes) {
       const home =
         myId != null && l.owner_id === myId && ids.has("me")
           ? "me"
@@ -959,9 +974,9 @@ export function FileBrowser({
       ...[...extra.values()].sort((a, b) => a.label.localeCompare(b.label)),
     ];
     return { lanesOfHome: map, userRows: rows };
-  }, [homes, lanes, myId]);
+  }, [homes, placeLanes, myId]);
   const grouped = new Set([...lanesOfHome.values()].flat().map((l) => l.id));
-  const looseLanes = lanes.filter((l) => !grouped.has(l.id));
+  const looseLanes = placeLanes.filter((l) => !grouped.has(l.id));
   // A home holding the open workspace shows it, whatever was stored.
   const homeIsOpen = (id: string, own: Lane[]) =>
     openHomes.has(id) ||
@@ -1687,9 +1702,7 @@ export function FileBrowser({
                 </MenuItem>
               )}
               {isHtml(menuItem) && menuTargets.length === 1 && (
-                <MenuItem onSelect={close(() => download([menuItem]))}>
-                  {t("fx.download")}
-                </MenuItem>
+                <MenuItem onSelect={close(() => download([menuItem]))}>{t("fx.download")}</MenuItem>
               )}
               <MenuSeparator />
               {!ro && (

client/src/components/lanes/WorkspaceRow.tsx

@@ -161,12 +161,19 @@ export function WorkspaceRow({
             e.preventDefault();
             onReorder(index, index + (e.key === "ArrowUp" ? -1 : 1));
           }}
-          title={`${lane.cwd}\n${readOnly ?? t("row.hint")}`}
+          title={`${lane.cwd}\n${lane.folder_missing ? t("row.folderMissing") : (readOnly ?? t("row.hint"))}`}
           className="flex min-w-0 flex-1 items-center gap-2 py-1.5 text-left"
         >
           <span aria-hidden className={`h-2 w-2 shrink-0 rounded-full ${workspaceDot(lane)}`} />
           <span className="sr-only">{t(`row.state.${workspaceDotLabel(lane)}`)}</span>
-          <span className="truncate text-[13px] font-medium text-fg-primary">{name}</span>
+          <span
+            data-folder-missing={lane.folder_missing ? "true" : undefined}
+            className={`truncate text-[13px] font-medium ${
+              lane.folder_missing ? "text-fg-muted line-through" : "text-fg-primary"
+            }`}
+          >
+            {name}
+          </span>
         </button>
       )}
       {readOnly && <Eye aria-label={readOnly} className="mr-1 h-3 w-3 shrink-0 text-fg-muted" />}

client/src/components/lanes/__tests__/FileExplorer.test.tsx

@@ -459,6 +459,33 @@ describe("FileExplorer", () => {
     );
   });
 
+  it("leaves a workspace whose folder was deleted out of the places", async () => {
+    vi.mocked(api.lanes.list).mockResolvedValue({
+      lanes: [
+        { id: 1, title: "one", cwd: "/w/one" },
+        { id: 2, title: "two", cwd: "/w/two", folder_missing: true },
+      ],
+      counts: {},
+    } as never);
+    open();
+    await screen.findByText("a.txt");
+    await waitFor(() => expect(api.lanes.list).toHaveBeenCalled());
+    await screen.findByText("one", { selector: "aside span" });
+    expect(screen.queryByRole("button", { name: "two" })).toBeNull();
+  });
+
+  it("drops the last folder's entries when the next one cannot be read", async () => {
+    vi.mocked(api.files.list).mockImplementation(async (_t, p = "") => {
+      if (p === "src") throw new Error("ENOENT: no such file or directory");
+      return root;
+    });
+    open();
+    await screen.findByText("a.txt");
+    fireEvent.doubleClick(row("src"));
+    await screen.findByText(/ENOENT/);
+    expect(screen.queryByText("a.txt")).toBeNull();
+  });
+
   it("right-clicks a sidebar workspace and a path crumb", async () => {
     const user = userEvent.setup();
     open();