fix(directory-explorer): clear selections on Finder pick; dedup VS Code batch

Two findings from the openchamber-bot review at 478f1e9c:

1. Pending selections silently swallowed the Open-in-Finder pick
   (prev #4). handleOpenInFinder flows into the batch-first branch of
   finalizeSelection, so with checkboxes ticked the OS pick was
   ignored and the selections were added instead. Clear selectedPaths
   before finalizeSelection so the Finder-sourced target is honored.

2. Within-batch dedup was missing in the VS Code branch (nit from
   the previous review). A path repeated within one batch hit
   addWorkspaceFolder twice. Mirror the non-VS Code contract with
   a seen Set; add a regression test asserting the host is called
   once per unique path.

packages/ui/src/components/session/DirectoryExplorerDialog.tsx

@@ -555,6 +555,9 @@ export const DirectoryExplorerDialog: React.FC<DirectoryExplorerDialogProps> = (
         return;
       }
 
+      // Clear pending selections so the Finder-sourced target is honored
+      // instead of silently being absorbed by the batch branch.
+      setSelectedPaths([]);
       await finalizeSelection(result.path);
     } catch (error) {
       toast.error(t('directoryExplorerDialog.toast.failedToSelectDirectory'), {

packages/ui/src/stores/useProjectsStore.ts

@@ -658,9 +658,13 @@ export const useProjectsStore = create<ProjectsStore>()(
       if (isVSCodeProjectsRuntime) {
         // VS Code paths are added via runtimeApis.vscode.addWorkspaceFolder,
         // which is reached only by addProject. Iterate so valid selections
-        // succeed instead of silently returning [].
+        // succeed instead of silently returning []. Dedupe by path so the
+        // returned array mirrors the non-VS Code contract.
         const added: ProjectEntry[] = [];
+        const seen = new Set<string>();
         for (const path of paths) {
+          if (seen.has(path)) continue;
+          seen.add(path);
           const project = await get().addProject(path);
           if (project) {
             added.push(project);

packages/ui/src/stores/useProjectsStore.vscodeAddProject.test.ts

@@ -157,4 +157,20 @@ describe('issue #2582: addProject in the VS Code runtime', () => {
     // final projects state (covered by the dedicated addProject tests).
     expect(added.length).toBeGreaterThanOrEqual(1);
   });
+
+  test('addProjects dedupes paths within a single batch in the VS Code runtime', async () => {
+    // A path repeated within one batch must hit the extension host once,
+    // not twice — mirrors the non-VS Code contract (seenPaths Set).
+    addWorkspaceFolderCalls.length = 0;
+    await useProjectsStore.getState().addProjects([
+      '/home/user/project-a',
+      '/home/user/project-a',
+      '/home/user/project-b',
+    ]);
+
+    expect(addWorkspaceFolderCalls).toEqual([
+      '/home/user/project-a',
+      '/home/user/project-b',
+    ]);
+  });
 });