Add extended diagnostics logging

- Electron crash handlers (render-process-gone, child-process-gone,
  unresponsive/responsive, process warnings) with a circuit-breaker
  auto-reload for renderer crashes
- Renderer error capture (window.onerror, unhandledrejection, React
  ErrorBoundary) forwarded to the main log via a one-way IPC channel
- Memory-pressure heartbeat measured against the V8 heap_size_limit
- Gated DEBUG log level (RD_DEBUG) and an in-memory ring of recent
  WARN/ERROR lines, exposed via the /errors endpoint and support bundle
- Disk-error classification (ENOSPC etc.) on download failures and
  integrity-check pass/fail logging

src/shared/ipc.ts

@@ -66,5 +66,6 @@ export const IPC_CHANNELS = {
   SET_PACKAGE_PRIORITY: "queue:set-package-priority",
   SKIP_ITEMS: "queue:skip-items",
   RESET_ITEMS: "queue:reset-items",
-  START_ITEMS: "queue:start-items"
+  START_ITEMS: "queue:start-items",
+  LOG_RENDERER_ERROR: "log:renderer-error"
 } as const;

src/shared/preload-api.ts

@@ -9,6 +9,7 @@ import type {
   DuplicatePolicy,
   HistoryEntry,
   PackagePriority,
+  RendererErrorReport,
   SessionStats,
   StartConflictEntry,
   StartConflictResolutionResult,
@@ -85,6 +86,7 @@ export interface ElectronApi {
   skipItems: (itemIds: string[]) => Promise<void>;
   resetItems: (itemIds: string[]) => Promise<void>;
   startItems: (itemIds: string[]) => Promise<void>;
+  reportRendererError: (report: RendererErrorReport) => void;
   onStateUpdate: (callback: (snapshot: UiSnapshot) => void) => () => void;
   onClipboardDetected: (callback: (links: string[]) => void) => () => void;
   onUpdateInstallProgress: (callback: (progress: UpdateInstallProgress) => void) => () => void;

src/shared/types.ts

@@ -499,3 +499,13 @@ export interface HistoryState {
   entries: HistoryEntry[];
   maxEntries: number;
 }
+
+export interface RendererErrorReport {
+  kind: "error" | "unhandledrejection" | "react";
+  message: string;
+  stack?: string;
+  source?: string;
+  line?: number;
+  column?: number;
+  componentStack?: string;
+}