fix(project-tree): refresh expanded excluded folders when files change

The watcher drops changes inside excluded and ignored folders so the index and
version control don't react to build output. That also kept an expanded `target`
from showing files a build added or removed. Those folders are now reported in
their own event, which only the Project view handles, and only for folders it has
loaded. Changes to existing files aren't reported, since the listing stays the same.

src/bindings.ts

@@ -3379,6 +3379,8 @@ export type IdeEvent =
 { type: "windowGroupsChanged" } | 
 /**  Files or directories changed on disk (after debouncing, ignore rules applied). */
 { type: "fsChanged"; created: IpcPath[]; modified: IpcPath[]; removed: IpcPath[] } | 
+/**  Excluded or ignored folders whose contents changed; they stay out of `FsChanged`. */
+{ type: "excludedDirsChanged"; dirs: IpcPath[] } | 
 /**
  *  The backend changed a document (reload from disk, formatting, refactoring).
  *  The UI applies `changes` on top of `base_version`, yielding `version`.

src/features/project-tree/index.ts

@@ -22,7 +22,15 @@ import { ProjectHeaderActions, useProjectHeaderMenu, useProjectTitleMenu } from
 import { loadHomeDir } from "./home";
 import { selectedNodes } from "./operations";
 import { ProjectView } from "./ProjectView";
-import { applyFsChange, initProjectTree, reloadAll, setChangedFiles, setOpenFiles, useProjectTree } from "./store";
+import {
+  applyFsChange,
+  initProjectTree,
+  reloadAll,
+  reloadLoadedDirs,
+  setChangedFiles,
+  setOpenFiles,
+  useProjectTree,
+} from "./store";
 
 export function activate(): () => void {
   loadHomeDir();
@@ -138,6 +146,7 @@ export function activate(): () => void {
         .map((n) => n.path),
     ),
     onIdeEvent("fsChanged", (e) => void applyFsChange(e)),
+    onIdeEvent("excludedDirsChanged", (e) => void reloadLoadedDirs(e.dirs)),
   ];
   return () => {
     disposers.reverse().forEach((d) => d());

src/features/project-tree/store.test.ts

@@ -3,6 +3,7 @@ import { MemoryFs, setProjectFsForTests } from "./fs";
 import { visibleInfo } from "./model";
 import {
   applyFsChange,
+  reloadLoadedDirs,
   currentModel,
   expandAll,
   initProjectTree,
@@ -75,6 +76,20 @@ describe("lazy loading", () => {
   });
 });
 
+describe("refresh of excluded folders", () => {
+  it("reloads only the folders the tree has loaded", async () => {
+    await loadDir(ROOT);
+    await loadDir("/p/docs");
+    const spy = vi.spyOn(fs, "readDir");
+
+    await reloadLoadedDirs(["/p/docs", "/p/target/never-opened"]);
+
+    expect(spy).toHaveBeenCalledTimes(1);
+    expect(spy).toHaveBeenCalledWith("/p/docs");
+    spy.mockRestore();
+  });
+});
+
 describe("refresh on fsChanged", () => {
   it("reloads affected loaded folders and keeps expansion and selection", async () => {
     await loadDir(ROOT);

src/features/project-tree/store.ts

@@ -451,6 +451,12 @@ export async function applyFsChange(event: { created: string[]; modified: string
   await Promise.all(plan.reload.map((p) => loadDir(p, true)));
 }
 
+/** Re-reads the folders among `dirs` the tree has loaded; the rest stay unread. */
+export async function reloadLoadedDirs(dirs: readonly string[]) {
+  const { listings } = get();
+  await Promise.all(dirs.filter((p) => listings.has(p)).map((p) => loadDir(p, true)));
+}
+
 /** Re-reads every loaded folder (View › Reload from Disk). */
 export async function reloadAll() {
   const { listings } = get();