feat(diag): E2EE investigation kit for the KE-1→4 cluster

LOTUS_E2EE_INVESTIGATION.md: per-KE capture runbook (console signatures, synapse
log greps + SQL against the documented LXC deployment, the KE-1⇒KE-2 causality
decision tree, ranked remediations incl. what a crypto-store reset wipes; SDK
finding: stable 41.6.0 has no OTK fix over our RC pin). Client: capture-only
console ring buffer (cryptoDiagLog, KE-signature-matched, max 200) + a Crypto
Diagnostics card in Developer Tools with a download-report button. ClientRoot
installs the capture hook at module load and mounts useSessionSync (cross-tab
sessions, prior commit).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/features/settings/developer-tools/DevelopTools.tsx

@@ -13,6 +13,7 @@ import {
 } from '../../../components/AccountDataEditor';
 import { copyToClipboard } from '../../../utils/dom';
 import { AccountData } from './AccountData';
+import { CryptoDiagnostics } from '../developer/CryptoDiagnostics';
 
 type DeveloperToolsProps = {
   requestClose: () => void;
@@ -109,6 +110,7 @@ export function DeveloperTools({ requestClose }: DeveloperToolsProps) {
                     />
                   </SequenceCard>
                 )}
+                {developerTools && <CryptoDiagnostics />}
               </Box>
               {developerTools && (
                 <AccountData