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/app/utils/cryptoDiagLog.ts

@@ -5,7 +5,7 @@ import pkg from '../../../package.json';
 //
 // Installs pass-through wrappers around `console.warn` / `console.error` that
 // ring-buffer any log line matching the KE-1..KE-4 bug-cluster signatures
-// (see LOTUS_E2EE_INVESTIGATION.md). It NEVER swallows a log call — the
+// (E2EE KE-1..4 capture; see LOTUS_TODO.md). It NEVER swallows a log call — the
 // original console method is always invoked — and it performs NO network I/O.
 // The report metadata is limited to SDK version / device id / user id / sync
 // state; the captured log lines themselves are intentional evidence and may