fix(ui): Make read-only content selectable with a Copy context menu (#48)

Root cause: body is user-select: none and each feature had to opt back in; the Markdown preview (and other read-only views) never did, and the app-wide contextmenu guard left no Copy item.
Fix: shared selectableText class (src/ui) for read-only content, and a fallback Copy context menu from browserGuards when right-clicking a selection or a selectable area (component menus still win).
Siblings covered: Quick Documentation / hover / completion docs, hover errors, Quick Definition, debugger value tooltip, inspection messages, message dialogs (no drag on body text), notification titles, About dialog; existing selectable consoles now get Copy too.
Verified in-app on macOS: select in Markdown preview, right-click Copy puts the text on the clipboard; tab context menu unchanged.

Claude-Session: https://claude.ai/code/session_01VUYsdXA2nkF5v6zsC93dpn

src/workbench/browserGuards.test.ts

@@ -0,0 +1,59 @@
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import { hideContextMenu, selectableText, showContextMenu, useContextMenuStore } from "@/ui";
+import { installBrowserGuards } from "./browserGuards";
+
+let dispose: () => void;
+
+beforeEach(() => {
+  dispose = installBrowserGuards({ blockReload: false });
+});
+
+afterEach(() => {
+  dispose();
+  hideContextMenu();
+  window.getSelection()?.removeAllRanges();
+  document.body.innerHTML = "";
+});
+
+function rightClick(el: Element) {
+  const e = new MouseEvent("contextmenu", { bubbles: true, cancelable: true, clientX: 5, clientY: 6 });
+  el.dispatchEvent(e);
+  return e;
+}
+
+describe("browser guards: context menu", () => {
+  it("never shows the native menu, and nothing on chrome", () => {
+    document.body.innerHTML = `<button id="b">Run</button>`;
+    const e = rightClick(document.getElementById("b")!);
+    expect(e.defaultPrevented).toBe(true);
+    expect(useContextMenuStore.getState().menu).toBeNull();
+  });
+
+  it("shows Copy on selectable read-only text (issue #36)", () => {
+    document.body.innerHTML = `<div class="${selectableText}"><p id="p">Hello</p></div>`;
+    const range = document.createRange();
+    range.selectNodeContents(document.getElementById("p")!);
+    window.getSelection()!.addRange(range);
+    const e = rightClick(document.getElementById("p")!);
+    expect(e.defaultPrevented).toBe(true);
+    const menu = useContextMenuStore.getState().menu;
+    expect(menu).toMatchObject({ x: 5, y: 6 });
+    expect(menu!.items[0]).toMatchObject({ label: "Copy", disabled: false });
+  });
+
+  it("keeps a component's own context menu", () => {
+    document.body.innerHTML = `<div class="${selectableText}"><p id="p">Hello</p></div>`;
+    const p = document.getElementById("p")!;
+    p.addEventListener("contextmenu", (e) => showContextMenu(e, [{ label: "Own" }]));
+    rightClick(p);
+    expect(useContextMenuStore.getState().menu!.items[0]).toMatchObject({ label: "Own" });
+  });
+
+  it("keeps out when a handler already prevented the default", () => {
+    document.body.innerHTML = `<div class="${selectableText}"><p id="p">Hello</p></div>`;
+    const p = document.getElementById("p")!;
+    p.addEventListener("contextmenu", (e) => e.preventDefault());
+    rightClick(p);
+    expect(useContextMenuStore.getState().menu).toBeNull();
+  });
+});

src/workbench/browserGuards.ts

@@ -2,8 +2,10 @@
  * Makes the webview behave like a desktop app: never the browser context menu
  * (its Reload/AutoFill items would act on the webview), no reload/print/
  * save-page/history shortcuts, no navigation on file drop. Copy/paste/undo
- * shortcuts stay untouched.
+ * shortcuts stay untouched. A right-click no component handled on selected or
+ * selectable read-only text gets IDEA's Copy menu instead of nothing.
  */
+import { copyMenuFor, showContextMenu, useContextMenuStore } from "@/ui";
 
 const BLOCKED = new Set([
   "Meta+P",
@@ -35,7 +37,17 @@ function keyId(e: KeyboardEvent) {
 
 export function installBrowserGuards(opts: { blockReload?: boolean } = {}): () => void {
   const blockReload = opts.blockReload ?? import.meta.env.PROD;
-  const onContextMenu = (e: MouseEvent) => e.preventDefault();
+  let menuBefore: unknown = null;
+  const beforeContextMenu = () => {
+    menuBefore = useContextMenuStore.getState().menu;
+  };
+  const onContextMenu = (e: MouseEvent) => {
+    const handled = e.defaultPrevented || useContextMenuStore.getState().menu !== menuBefore;
+    e.preventDefault();
+    if (handled) return;
+    const items = copyMenuFor(e.target);
+    if (items) showContextMenu(e, items);
+  };
   const onKeyDown = (e: KeyboardEvent) => {
     const id = keyId(e);
     if (BLOCKED.has(id) || (blockReload && RELOAD.has(id))) e.preventDefault();
@@ -43,11 +55,13 @@ export function installBrowserGuards(opts: { blockReload?: boolean } = {}): () =
   const onDrag = (e: DragEvent) => {
     if (!(e.target as Element | null)?.closest?.("[data-drop-target]")) e.preventDefault();
   };
+  window.addEventListener("contextmenu", beforeContextMenu, true);
   window.addEventListener("contextmenu", onContextMenu);
   window.addEventListener("keydown", onKeyDown);
   window.addEventListener("dragover", onDrag);
   window.addEventListener("drop", onDrag);
   return () => {
+    window.removeEventListener("contextmenu", beforeContextMenu, true);
     window.removeEventListener("contextmenu", onContextMenu);
     window.removeEventListener("keydown", onKeyDown);
     window.removeEventListener("dragover", onDrag);