feat(crypto) + docs: request persistent storage; consolidate docs to 3

- index.tsx: request navigator.storage.persist() for logged-in sessions so the
  browser can't evict the IndexedDB rust-crypto store (eviction while the
  localStorage session survives resurrects the device with a blank store → the
  KE-1 "one time key already exists" upload storm). Guarded, checks persisted()
  first, best-effort.
- Docs: remove HANDOFF_ELEMENT_CALL_FORK.md, LOTUS_E2EE_INVESTIGATION.md, and
  LOTUS_BUGS.md. Port their live content into the three kept docs — verification
  backlog → LOTUS_TESTING; open bugs + E2EE (KE-1..4) + an Element Call fork
  operational reference (publish steps + io.lotus action catalog) → LOTUS_TODO.
  Fix all dangling references (README, code comments, cross-doc links). Full
  history of the removed docs remains in git.

Gates: tsc/eslint/prettier clean, build OK, 665 tests.

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

src/index.tsx

@@ -44,6 +44,20 @@ if ('serviceWorker' in navigator) {
   });
 }
 
+// Request persistent storage so the browser can't evict the IndexedDB
+// rust-crypto store under storage pressure. Eviction (while the localStorage
+// session/device-id survives) resurrects the device with a blank crypto store,
+// which then re-uploads OTKs the server already holds → the "one time key
+// already exists" upload storm and E2EE breakage. Only ask for sessions worth
+// protecting (skip anonymous/landing visitors to avoid a needless Firefox
+// prompt); check persisted() first so we don't re-prompt. Best-effort.
+if (navigator.storage?.persist && getFallbackSession()) {
+  navigator.storage
+    .persisted()
+    .then((already) => (already ? undefined : navigator.storage.persist()))
+    .catch(() => undefined);
+}
+
 // Reload once if a lazy-loaded chunk is missing (stale deployment)
 window.addEventListener('vite:preloadError', () => {
   if (!sessionStorage.getItem('chunk-reload-attempted')) {