Improve attachment memory safety, downloads, and high-memory alert UX.

Stream large receives to disk with chunk acks to cap renderer RAM, evict
off-screen display blobs, and route exports through a disk-aware download
service. Fix the high-memory dialog (backdrop dismiss, copy, log actions),
allow diagnostics paths in the path jail, and restore persisted image
hydration after reload.

Co-authored-by: Cursor <cursoragent@cursor.com>

toju-app/public/i18n/en.json

@@ -18,8 +18,10 @@
     },
     "highMemoryAlert": {
       "badge": "High memory usage",
-      "title": "The app used {{usageGb}} GB of RAM last session",
-      "message": "A diagnostics log was saved in your app data folder. You can open it now or copy the path if you want to share it with support.",
+      "thresholdTitle": "The app is using {{usageGb}} GB of RAM",
+      "thresholdMessage": "MetoYou crossed the 2 GB memory threshold. A diagnostics log was saved so you can inspect what was using memory or share it with support.",
+      "manualTitle": "RAM diagnostics exported ({{usageGb}} GB in use)",
+      "manualMessage": "A snapshot of current memory usage was saved. Open the log, reveal it in your file manager, or copy the path to share with support.",
       "openLog": "Open log file",
       "showInFolder": "Show in folder",
       "copyPath": "Copy path",
@@ -1507,7 +1509,9 @@
       "title": "App-wide debugging",
       "description": "Capture UI events, navigation activity, console output, and global runtime errors in a live debug console.",
       "processRam": "Process RAM",
-      "ramHint": "Live total working set from Electron app metrics. Updates every 2 seconds.",
+      "exportRamDiagnostics": "Export RAM diagnostics",
+      "exportRamDiagnosticsWorking": "Exporting...",
+      "ramHint": "Live total working set from Electron app metrics. Updates every 2 seconds. Export saves a diagnostics log and opens the high-memory alert dialog.",
       "capturedEvents": "Captured events",
       "lastUpdate": "Last update: {{label}}",
       "noLogsYet": "No logs yet",