feat: coordinate bounded renderer startup recovery

Retry the initial renderer load once, then resolve repeated failures through a visible safe surface or a controlled close.

Bound renderer crash reloads until a successful ready signal resets recovery, keep terminal handling idempotent, and cover retries, fallback failures, reload failures, ready resets, and late events with focused tests.

lib/startup-renderer.js

@@ -8,6 +8,68 @@ function resolveStartupLanguage(config) {
   return config && config.globalSettings && config.globalSettings.language === 'de' ? 'de' : 'en';
 }
 
+function createStartupRecoveryCoordinator({ load, reload, reveal, showFailure, close }) {
+  let initialLoad;
+  let crashReloads = 0;
+  let terminalFailure;
+
+  function endWithFailure(failure) {
+    if (!terminalFailure) {
+      terminalFailure = (async () => {
+        if (typeof showFailure !== 'function') {
+          await close(failure);
+          return;
+        }
+        try {
+          await showFailure(failure);
+          reveal();
+        } catch (surfaceError) {
+          await close({ ...failure, surfaceError });
+        }
+      })();
+    }
+    return terminalFailure;
+  }
+
+  return {
+    loadInitial(...args) {
+      if (terminalFailure) return terminalFailure;
+      if (!initialLoad) {
+        initialLoad = (async () => {
+          for (let attempt = 1; attempt <= 2; attempt++) {
+            try {
+              return await load(...args);
+            } catch (error) {
+              if (attempt === 2) {
+                await endWithFailure({ phase: 'initial-load', attempt, error });
+              }
+            }
+          }
+        })();
+      }
+      return initialLoad;
+    },
+    async rendererCrashed(details) {
+      if (terminalFailure) return terminalFailure;
+      if (crashReloads >= 1) {
+        return endWithFailure({ phase: 'renderer-crash', attempt: crashReloads + 1, details });
+      }
+      crashReloads++;
+      try {
+        await reload();
+      } catch (error) {
+        return endWithFailure({ phase: 'renderer-reload', attempt: crashReloads, details, error });
+      }
+    },
+    rendererReady() {
+      if (terminalFailure) return false;
+      crashReloads = 0;
+      reveal();
+      return true;
+    }
+  };
+}
+
 function createStartupWindow(BrowserWindow, options) {
   const window = new BrowserWindow({ ...options, show: false });
   window.once('ready-to-show', () => {
@@ -22,4 +84,9 @@ function createStartupWindow(BrowserWindow, options) {
   };
 }
 
-module.exports = { configureStartupRenderer, createStartupWindow, resolveStartupLanguage };
+module.exports = {
+  configureStartupRenderer,
+  createStartupRecoveryCoordinator,
+  createStartupWindow,
+  resolveStartupLanguage
+};