fix(project): keep attachments in the current project (#2320)

Attach adds a trusted folder to the current project without reopening it or moving its root. Attachments live in the primary project's private .openidea/workspace.json, and detaching the last one restores a plain project.

ProjectInfo.name stays the primary project's name; displayName supplies window titles, project tabs and Recent Projects. Attach is no longer a remembered opening policy, and File > Attach Project is available when the policy is not Ask. Attached folders must be trusted, and Restricted Mode names any attached folder that blocks trust. Explicit workspaces keep their behaviour and still cannot be created in or inside a linked project.

src/workbench/projectWindow.ts

@@ -6,10 +6,10 @@ import { connectRemote, isRemoteWindow } from "@/platform/remote";
 import { ask } from "./messages";
 import { maybeEditorService } from "./contributions";
 
-/** "Open project in": `new` | `same` | `attach` | `ask`. */
-export function openPolicy(): "ask" | "new" | "same" | "attach" {
+/** "Open project in": `new` | `same` | `ask`. */
+export function openPolicy(): "ask" | "new" | "same" {
   const v = useProject.getState().settings?.general?.openProjectIn;
-  return v === "new" || v === "same" || v === "attach" ? v : "ask";
+  return v === "new" || v === "same" ? v : "ask";
 }
 
 /**
@@ -21,8 +21,7 @@ export async function chooseProjectWindow(name: string, allowAttach = true): Pro
   const { project, lightEdit } = useProject.getState();
   if (!project && !lightEdit) return "same";
   const canAttach = allowAttach && !!project && !isRemoteWindow();
-  const policy = openPolicy();
-  const mode = policy === "attach" && !canAttach ? "ask" : policy;
+  const mode = openPolicy();
   if (mode !== "ask") return mode;
   const r = await ask({
     title: t("app.window.askTitle"),
@@ -37,7 +36,7 @@ export async function chooseProjectWindow(name: string, allowAttach = true): Pro
     checkbox: t("app.window.askRemember"),
   });
   if (r.button !== "same" && r.button !== "new" && r.button !== "attach") return null;
-  if (r.checked) {
+  if (r.checked && r.button !== "attach") {
     try {
       useProject.setState({
         settings: await call(commands.settingsSet("global", "general.openProjectIn", JSON.stringify(r.button))),