[eric] browser: Chrome-style suspend capsules (sessionStorage+scroll survive), last-visible-frame snapshots, 20s working grace

frontend/src/shared/browserStateCapsule.ts

@@ -0,0 +1,58 @@
+import type { BrowserWebview } from './browserRegistry';
+
+// Capsules carry site session tokens: in-memory ONLY, never redux, never disk, never logged.
+export interface TabCapsule {
+  ss: Record<string, string>;
+  sx: number;
+  sy: number;
+  origin: string;
+  capturedAt: number;
+}
+
+const CAPSULE_CAP = 100;
+const CAPTURE_TIMEOUT_MS = 800;
+const capsules = new Map<string, TabCapsule>();
+
+interface OpenswarmCapsuleBridge {
+  setSessionCapsule?: (wcId: number, capsule: TabCapsule) => void;
+}
+
+/** Snapshot a tab's sessionStorage + scroll before its webview unmounts, so resume can restore it Chrome-style instead of logging the user out. */
+export async function captureTabCapsule(wv: BrowserWebview | null | undefined, tabId: string): Promise<void> {
+  if (!wv) return;
+  try {
+    const raw = await Promise.race([
+      wv.executeJavaScript(
+        `(() => { const ss = {}; for (let i = 0; i < sessionStorage.length; i++) { const k = sessionStorage.key(i); if (k !== null) ss[k] = sessionStorage.getItem(k); } return JSON.stringify({ ss, sx: window.scrollX, sy: window.scrollY, origin: location.origin }); })()`,
+      ),
+      new Promise<null>((resolve) => setTimeout(() => resolve(null), CAPTURE_TIMEOUT_MS)),
+    ]);
+    if (typeof raw !== 'string') return;
+    const parsed = JSON.parse(raw) as { ss: Record<string, string>; sx: number; sy: number; origin: string };
+    if (!parsed.origin || !parsed.origin.startsWith('http')) return;
+    capsules.set(tabId, { ss: parsed.ss, sx: parsed.sx, sy: parsed.sy, origin: parsed.origin, capturedAt: Date.now() });
+    if (capsules.size > CAPSULE_CAP) {
+      const oldest = [...capsules.entries()].sort((a, b) => a[1].capturedAt - b[1].capturedAt)[0];
+      if (oldest) capsules.delete(oldest[0]);
+    }
+  } catch {
+    // A dead/navigating webview just means no capsule; resume falls back to a plain reload.
+  }
+}
+
+/** Hand a resumed tab's capsule to the main process, keyed by the fresh webContents id, BEFORE loadURL fires; the guest preload sync-takes it at document-start so page scripts see restored state. */
+export function registerCapsuleForRestore(wv: BrowserWebview, tabId: string): void {
+  const capsule = capsules.get(tabId);
+  if (!capsule) return;
+  const bridge = (window as unknown as { openswarm?: OpenswarmCapsuleBridge }).openswarm;
+  if (!bridge?.setSessionCapsule) return;
+  try {
+    bridge.setSessionCapsule(wv.getWebContentsId(), capsule);
+  } catch {
+    // Bridge unavailable (iframe fallback / non-Electron): plain reload, same as before capsules existed.
+  }
+}
+
+export function hasCapsule(tabId: string): boolean {
+  return capsules.has(tabId);
+}