Edit workspace files directly on web (#2270)

* feat(files): edit workspace files on web

Keep source buffers synchronized with host file changes and require an explicit overwrite or reload when revisions diverge.

* feat(panels): surface and protect modified tabs

Expose tooltip and modification state through the generic panel boundary so tabs can show stable metadata and guard every close route consistently.

* fix(tests): use portable fake timeout handle

* fix(files): harden editor conflict handling

Preserve modified panel state across tab eviction, use precise revisions for optimistic writes, coalesce concurrent file watchers, and localize the editor interface.

* fix(files): close editor concurrency gaps

Coalesce clean reloads, preserve subscriber identities and file permissions, suspend pending saves during close confirmation, and carry precise revisions through file reads.

* test(files): expect read revision metadata

packages/app/src/panels/panel-instance-attributes.test.ts

@@ -0,0 +1,35 @@
+import { describe, expect, test } from "vitest";
+import {
+  getPanelInstanceAttributes,
+  setPanelInstanceAttributes,
+  subscribePanelInstanceAttributes,
+} from "./panel-instance-attributes";
+
+describe("panel instance attributes", () => {
+  test("keeps runtime attributes isolated by workspace and tab", () => {
+    const first = { serverId: "server", workspaceId: "one", tabId: "tab" };
+    const second = { serverId: "server", workspaceId: "two", tabId: "tab" };
+
+    setPanelInstanceAttributes(first, { modified: true });
+
+    expect(getPanelInstanceAttributes(first)).toEqual({ modified: true });
+    expect(getPanelInstanceAttributes(second)).toEqual({ modified: false });
+
+    setPanelInstanceAttributes(first, { modified: false });
+  });
+
+  test("notifies subscribers only when attributes change", () => {
+    const identity = { serverId: "server", workspaceId: "workspace", tabId: "observed" };
+    let notifications = 0;
+    const unsubscribe = subscribePanelInstanceAttributes(identity, () => {
+      notifications += 1;
+    });
+
+    setPanelInstanceAttributes(identity, { modified: true });
+    setPanelInstanceAttributes(identity, { modified: true });
+    setPanelInstanceAttributes(identity, { modified: false });
+
+    expect(notifications).toBe(2);
+    unsubscribe();
+  });
+});