refactor: address code-review findings for install detection and diag log

- pwa-install.ts: permanent 'ponomar-ever-installed' marker keeps install
  button hidden on Firefox/Safari after appinstalled clears the offer flag;
  isPwaInstalled moved to core for reuse
- diag-log: self-heal corrupted storage, show MM-DD in tail
- settings: refresh diag panel after clear-cache; uniform completion style
- data-cache.has: plain count(key); document HTML-as-failure intent

src/core/data-cache.ts

@@ -102,7 +102,7 @@ export class DataCache {
       const db = await getDB();
       return await new Promise<boolean | null>((resolve) => {
         const tx = db.transaction(STORE_NAME, 'readonly');
-        const request = tx.objectStore(STORE_NAME).count(IDBKeyRange.only(key));
+        const request = tx.objectStore(STORE_NAME).count(key);
         request.onsuccess = () => resolve(request.result > 0);
         request.onerror = () => resolve(null);
       });

src/core/diag-log.ts

@@ -15,10 +15,21 @@ export interface DiagEvent {
   [key: string]: unknown;
 }
 
+function readEvents(): DiagEvent[] {
+  const raw = localStorage.getItem(DIAG_KEY);
+  if (!raw) return [];
+  try {
+    const arr = JSON.parse(raw);
+    if (Array.isArray(arr)) return arr as DiagEvent[];
+  } catch { /* fall through */ }
+  // Corrupted or non-array value — reset so logging can recover
+  localStorage.removeItem(DIAG_KEY);
+  return [];
+}
+
 export function diagLog(event: string, detail?: Record<string, unknown>) {
   try {
-    const raw = localStorage.getItem(DIAG_KEY);
-    const arr: DiagEvent[] = raw ? JSON.parse(raw) : [];
+    const arr = readEvents();
     arr.push({ t: new Date().toISOString(), event, ...(detail ?? {}) });
     while (arr.length > MAX_EVENTS) arr.shift();
     localStorage.setItem(DIAG_KEY, JSON.stringify(arr));
@@ -27,16 +38,16 @@ export function diagLog(event: string, detail?: Record<string, unknown>) {
 
 export function getDiagLog(): DiagEvent[] {
   try {
-    const raw = localStorage.getItem(DIAG_KEY);
-    const arr = raw ? JSON.parse(raw) : [];
-    return Array.isArray(arr) ? arr : [];
+    return readEvents();
   } catch {
     return [];
   }
 }
 
 function formatEvent(e: DiagEvent): string {
-  const time = (e.t || '').slice(11, 19);
+  // MM-DD HH:MM:SS (local relevance comes from ISO UTC; day boundary matters
+  // when events span days)
+  const time = `${(e.t || '').slice(5, 10)} ${(e.t || '').slice(11, 19)}`;
   const parts: string[] = [];
   for (const [k, v] of Object.entries(e)) {
     if (k === 't' || k === 'event') continue;

src/core/offline-manager.ts

@@ -188,6 +188,8 @@ export class OfflineManager {
           }
           if (!resp.ok) continue;
           const ct = resp.headers.get('content-type');
+          // HTML body (SPA fallback / captive portal) is not our data —
+          // counts as a failure and feeds the circuit-breaker streak
           if (ct && ct.includes('text/html')) break;
 
           let data: unknown;

src/core/pwa-install.ts

@@ -0,0 +1,46 @@
+/**
+ * PWA installation state detection.
+ *
+ * 'ponomar-ever-installed' is a permanent marker (never removed): set when
+ * the app is installed, launched in standalone mode, or inherited from the
+ * legacy 'ponomar-installed' offer flag. Used to hide the Settings install
+ * button on browsers without getInstalledRelatedApps() (Firefox, Safari).
+ * Distinct from 'ponomar-installed', which only gates the first-launch
+ * offline-offer modal and is cleared on appinstalled for re-offer semantics.
+ */
+
+const EVER_INSTALLED_KEY = 'ponomar-ever-installed';
+
+export function isStandaloneDisplay(): boolean {
+  return (
+    window.matchMedia('(display-mode: standalone)').matches ||
+    (window.navigator as any).standalone === true
+  );
+}
+
+export function markEverInstalled(): void {
+  try {
+    localStorage.setItem(EVER_INSTALLED_KEY, '1');
+  } catch { /* best-effort */ }
+}
+
+export function hasEverInstalledMarker(): boolean {
+  try {
+    return localStorage.getItem(EVER_INSTALLED_KEY) === '1';
+  } catch {
+    return false;
+  }
+}
+
+export async function isPwaInstalled(): Promise<boolean> {
+  if (isStandaloneDisplay()) return true;
+  if (hasEverInstalledMarker()) return true;
+  try {
+    const navAny = navigator as any;
+    if (typeof navAny.getInstalledRelatedApps === 'function') {
+      const apps = await navAny.getInstalledRelatedApps();
+      if (Array.isArray(apps) && apps.length > 0) return true;
+    }
+  } catch { /* not supported */ }
+  return false;
+}

src/ui/app.ts

@@ -12,6 +12,7 @@ import { loadSettings, type Settings } from './settings-view';
 import { getTranslations, type LanguageCode } from '../core/i18n';
 import { DataCache } from '../core/data-cache';
 import { diagLog } from '../core/diag-log';
+import { markEverInstalled, hasEverInstalledMarker } from '../core/pwa-install';
 
 type View = 'calendar' | 'bible' | 'prayer' | 'akathists' | 'parimii' | 'horologion' | 'sbornik' | 'paraclete' | 'irmologion' | 'menaion' | 'triodion' | 'lives' | 'settings';
 
@@ -139,13 +140,20 @@ export class App {
     // Clear first-launch flag on re-install
     window.addEventListener('appinstalled', () => {
       localStorage.removeItem('ponomar-installed');
+      markEverInstalled();
     });
 
     // Show offline offer on first standalone launch
     const isStandalone = () => window.matchMedia('(display-mode: standalone)').matches || (window.navigator as any).standalone;
-    if (isStandalone() && !localStorage.getItem('ponomar-installed')) {
-      localStorage.setItem('ponomar-installed', '1');
-      this.showOfflineOfferModal();
+    if (isStandalone()) {
+      markEverInstalled();
+      if (!localStorage.getItem('ponomar-installed')) {
+        localStorage.setItem('ponomar-installed', '1');
+        this.showOfflineOfferModal();
+      }
+    } else if (localStorage.getItem('ponomar-installed') && !hasEverInstalledMarker()) {
+      // One-time migration: legacy offer flag implies the app was installed
+      markEverInstalled();
     }
 
     // Auto-preload essential data for the current language

src/ui/settings-view.ts

@@ -6,6 +6,7 @@ import { getTranslations, type LanguageCode } from '../core/i18n';
 import { OfflineManager } from '../core/offline-manager';
 import { DataCache } from '../core/data-cache';
 import { diagTail } from '../core/diag-log';
+import { isPwaInstalled } from '../core/pwa-install';
 
 const LANGUAGES = [
   { code: 'en', name: 'English', local: 'English' },
@@ -417,7 +418,7 @@ export class SettingsView {
       if (!hintEl) return;
       const ua = navigator.userAgent;
       let hint: string;
-      if (await this.isPwaInstalled()) {
+      if (await isPwaInstalled()) {
         hint = t.settings.installPwaAlreadyInstalled;
       } else if (/firefox/i.test(ua)) {
         hint = t.settings.installPwaHintFirefox;
@@ -435,7 +436,7 @@ export class SettingsView {
       const btn = document.getElementById('install-pwa');
       if (!btn || !('serviceWorker' in navigator)) return;
       try {
-        if (!(await this.isPwaInstalled())) btn.classList.remove('hidden');
+        if (!(await isPwaInstalled())) btn.classList.remove('hidden');
       } catch { /* stay hidden */ }
     })();
 
@@ -602,6 +603,8 @@ export class SettingsView {
       if (statsEl) statsEl.textContent = t.settings.offlineCleared;
       const progressDiv = document.getElementById('offline-progress');
       if (progressDiv) progressDiv.classList.add('hidden');
+      const diagEl = document.getElementById('diag-log');
+      if (diagEl) diagEl.textContent = diagTail();
     });
 
     // Show initial storage stats
@@ -694,12 +697,14 @@ export class SettingsView {
         }).then((prog) => {
           if (progressBar) progressBar.style.width = '100%';
           if (progressText) {
-            const failList = prog.failedFiles?.length ? `: ${prog.failedFiles.join(', ')}` : '';
-            progressText.textContent = prog.aborted
-              ? t.settings.offlineAborted
-              : prog.failed > 0
-                ? `${t.settings.offlineDone} ${prog.failed} ${t.settings.offlineFailed}${failList}`
-                : t.settings.offlineDone;
+            if (prog.aborted) {
+              progressText.textContent = t.settings.offlineAborted;
+            } else if (prog.failed > 0) {
+              const failList = prog.failedFiles?.length ? `: ${prog.failedFiles.join(', ')}` : '';
+              progressText.textContent = `${t.settings.offlineDone} ${prog.failed} ${t.settings.offlineFailed}${failList}`;
+            } else {
+              progressText.textContent = t.settings.offlineDone;
+            }
           }
           const diagEl = document.getElementById('diag-log');
           if (diagEl) diagEl.textContent = diagTail();
@@ -737,19 +742,4 @@ export class SettingsView {
       preview.style.fontSize = `${this.settings.fontSize}px`;
     }
   }
-
-  private async isPwaInstalled(): Promise<boolean> {
-    if (window.matchMedia('(display-mode: standalone)').matches || (window.navigator as any).standalone === true) {
-      return true;
-    }
-    if (localStorage.getItem('ponomar-installed')) return true;
-    try {
-      const navAny = navigator as any;
-      if (typeof navAny.getInstalledRelatedApps === 'function') {
-        const apps = await navAny.getInstalledRelatedApps();
-        if (Array.isArray(apps) && apps.length > 0) return true;
-      }
-    } catch { /* not supported */ }
-    return false;
-  }
 }