feat: protect offline work from storage eviction (Closes #1110)

frontend/dashboard.js

@@ -7976,12 +7976,16 @@
       isIosSafari:() => isIosDevice && /Safari/.test(navigator.userAgent) && !/CriOS|FxiOS|EdgiOS|OPiOS/.test(navigator.userAgent),
     });
     installApp.start();
+    const deviceStorage = createDeviceStorage.mount(document);
+    await deviceStorage.start();
     deviceSetup = createMobileDeviceSetup.mount({
       document, installApp, promptStorage:localStorage,
       timerView,
       offlineAvailable:() => offlineStorageReady,
       offlineEnabled:() => offlineWorkStore.enabled(),
       enableOffline:() => setOfflineWorkEnabled(true),
+      storageProtectionReadiness:() => deviceStorage.persistenceReadiness(),
+      protectStorage:() => deviceStorage.requestPersistence(),
       enablePush:async () => {
         const controller = await pushControllerReady;
         if (!controller) return;
@@ -7998,7 +8002,6 @@
         await controller.enableDeadline();
       },
     });
-    await createDeviceStorage.mount(document).start();
     await deviceSetup.start();
     return deviceSetup;
   }

frontend/device-storage.js

@@ -21,6 +21,7 @@
   let privateRecordCount = 0;
   let inventoryUnavailable = false;
   let fullClearArmed = false;
+  let persistence = { state:'unavailable', detail:'Storage protection is unavailable in this browser.', label:'Unavailable' };
   const ownedCaches = async () => (await options.caches?.keys?.() || [])
     .filter(name => name.startsWith('stackchain-dashboard-'));
 
@@ -37,10 +38,48 @@
     return Math.round((Number(value) || 0) / (1024 * 1024));
   }
 
+  async function inspectPersistence() {
+    if (typeof options.storageManager?.persisted !== 'function' || typeof options.storageManager?.persist !== 'function') {
+      persistence = {state:'unavailable', detail:'Storage protection is unavailable in this browser.', label:'Unavailable'};
+      return persistence;
+    }
+    try {
+      const protectedStorage = await options.storageManager.persisted();
+      persistence = protectedStorage
+        ? {state:'complete', detail:'Offline work is protected from automatic browser storage cleanup.', label:'Protected'}
+        : {state:'incomplete', detail:'Offline work uses best-effort browser storage and may be removed under storage pressure.', label:'Best effort'};
+    } catch (_error) {
+      persistence = {state:'incomplete', detail:'Storage protection could not be checked. Retry to protect offline work.', label:'Check failed'};
+    }
+    return persistence;
+  }
+
+  function persistenceReadiness() {
+    return {state:persistence.state, detail:persistence.detail};
+  }
+
+  async function requestPersistence() {
+    if (typeof options.storageManager?.persist !== 'function') return persistenceReadiness();
+    let granted = false;
+    try { granted = await options.storageManager.persist(); }
+    catch (_error) {
+      persistence = {state:'incomplete', detail:'Storage protection request failed. Offline work still uses best-effort storage; retry when ready.', label:'Request failed'};
+      options.detail.textContent = options.detail.textContent.replace(/Storage protection: [^·]+/, 'Storage protection: Request failed ');
+      return persistenceReadiness();
+    }
+    await refresh();
+    if (!granted && persistence.state !== 'complete') {
+      persistence = {state:'incomplete', detail:'The browser did not grant storage protection. Offline work still works but may be removed under storage pressure.', label:'Denied'};
+      options.detail.textContent = options.detail.textContent.replace(/Storage protection: [^·]+/, 'Storage protection: Denied ');
+    }
+    return persistenceReadiness();
+  }
+
   async function refresh() {
     let estimate = null;
     try { estimate = await options.storageManager?.estimate?.(); }
     catch (_error) { /* Storage estimates are optional. */ }
+    await inspectPersistence();
     options.summary.textContent = estimate?.quota
       ? `${megabytes(estimate.usage)} MB of ${megabytes(estimate.quota)} MB browser storage used.`
       : 'Browser storage usage is unavailable.';
@@ -52,7 +91,7 @@
     privateRecordCount = inventory.recordCount;
     inventoryUnavailable = inventory.unavailable;
     const cacheCount = (await ownedCaches()).length;
-    options.detail.textContent = `${itemCount} private browser item${itemCount === 1 ? '' : 's'} · `
+    options.detail.textContent = `Storage protection: ${persistence.label} · ${itemCount} private browser item${itemCount === 1 ? '' : 's'} · `
       + `${inventoryUnavailable ? 'private work status unknown' : `${privateRecordCount} private work record${privateRecordCount === 1 ? '' : 's'}`} · `
       + `${cacheCount} cached app cop${cacheCount === 1 ? 'y' : 'ies'}`;
     return { itemCount, privateRecordCount, inventoryUnavailable, cacheCount };
@@ -84,7 +123,7 @@
       privateItemCount = 0;
       fullClearArmed = false;
       options.clearAllButton.textContent = 'Clear all private data';
-      options.detail.textContent = '0 private browser items · 0 private work records · 0 cached app copies';
+      options.detail.textContent = `Storage protection: ${persistence.label} · 0 private browser items · 0 private work records · 0 cached app copies`;
       options.summary.textContent = 'All Stackchain private data was cleared from this device.';
     } catch (error) {
       options.summary.textContent = `Private data was not fully cleared: ${error.message}`;
@@ -99,5 +138,5 @@
     return refresh();
   }
 
-  return { refresh, start };
+  return { refresh, start, persistenceReadiness, requestPersistence };
 });

frontend/index.html

@@ -112,6 +112,10 @@
         <div><strong>Keep work available offline</strong><p class="small" id="device-setup-offline-status" role="status"></p></div>
         <button class="device-setup-action" id="device-setup-offline" type="button">Enable</button>
       </li>
+      <li class="device-setup-step">
+        <div><strong>Protect offline work</strong><p class="small" id="device-setup-protection-status" role="status"></p></div>
+        <button class="device-setup-action" id="device-setup-protection" type="button">Protect</button>
+      </li>
       <li class="device-setup-step">
         <div><strong>Notify me about new updates</strong><p class="small" id="device-setup-push-status" role="status"></p></div>
         <button class="device-setup-action" id="device-setup-push" type="button">Enable</button>

frontend/mobile-device-setup.js

@@ -7,6 +7,7 @@
   const steps = [
     ['install', options.installButton, options.installStatus, options.install],
     ['offline', options.offlineButton, options.offlineStatus, options.enableOffline],
+    ['protection', options.protectionButton, options.protectionStatus, options.protectStorage],
     ['push', options.pushButton, options.pushStatus, options.enablePush],
     ['deadline', options.deadlineButton, options.deadlineStatus, options.enableDeadline],
   ];
@@ -108,8 +109,10 @@ function mountMobileDeviceSetup(options) {
     launcher:qs('#open-device-setup'), closeButton:qs('#close-device-setup'),
     sheet:qs('#device-setup-sheet'), installButton:qs('#device-setup-install'),
     offlineButton:qs('#device-setup-offline'), pushButton:qs('#device-setup-push'),
+    protectionButton:qs('#device-setup-protection'),
     deadlineButton:qs('#device-setup-deadline'),
     installStatus:qs('#device-setup-install-status'), offlineStatus:qs('#device-setup-offline-status'),
+    protectionStatus:qs('#device-setup-protection-status'),
     pushStatus:qs('#device-setup-push-status'), deadlineStatus:qs('#device-setup-deadline-status'),
     readyStatus:qs('#device-setup-ready-status'),
     promptCard:qs('#device-readiness-card'), promptSummary:qs('#device-readiness-summary'),
@@ -126,6 +129,7 @@ function mountMobileDeviceSetup(options) {
         : options.offlineEnabled()
           ? {state:'complete', detail:qs('#offline-work-status').textContent || 'Offline work is saved.'}
           : {state:'incomplete', detail:'Private My Work and Today data are not saved offline.'},
+      protection:options.storageProtectionReadiness(),
       push:qs('#push-updates').disabled
         ? {state:'unavailable', detail:qs('#push-update-status').textContent || 'Update notifications are unavailable.'}
         : qs('#push-updates').checked
@@ -135,6 +139,7 @@ function mountMobileDeviceSetup(options) {
     }),
     install:() => options.installApp.install(),
     enableOffline:options.enableOffline,
+    protectStorage:options.protectStorage,
     enablePush:options.enablePush,
     enableDeadline:options.enableDeadline,
   });

frontend/service-worker.js

@@ -1,7 +1,7 @@
 const BASE = new URL('./', self.location.href).pathname;
 importScripts(BASE + 'static/private-data-registry.js');
 importScripts(BASE + 'static/background-issue-sync.js');
-const CACHE = 'stackchain-dashboard-shell-v121';
+const CACHE = 'stackchain-dashboard-shell-v122';
 const OFFLINE_LEASE_URL = new URL(BASE + '__offline-session-lease', self.location.origin).href;
 const OUTAGE_STATUSES = new Set([500, 502, 503, 504]);
 const NAVIGATION_TIMEOUT_MS = self.__STACKCHAIN_NAVIGATION_TIMEOUT_MS || 4000;