fix(export): advance the raw pagination boundary on every event

Exporting a date range from an ENCRYPTED room over-paginated and mislabeled
"truncated": oldestRawTs (the how-far-back-have-we-paged boundary) was updated
only after the RoomMessage + decryption-failure filters, so undecryptable or
non-message old events never advanced it, the fromTs break never fired, and the
loop ran to MAX_EXPORT_PAGES. getTs() is unencrypted envelope metadata, so the
boundary update now runs for every event, above the filters.

Guarded with `ts > 0` so a bogus 0/negative origin_server_ts can't collapse the
boundary and cause the opposite failure — a silent early break / under-paginated
export (per review, silent omission in an export is worse than the loud
over-pagination this fixes). oldestTs (oldest collected in-range message) is
unchanged.

Two review agents (both confirmed getTs is decryption-independent, no
intra-page collection regression, oldestRawTs feeds only the fromTs break, no
plaintext regression); the second surfaced the 0-ts under-pagination edge, hence
the guard. Not unit-testable (embedded component + needs an E2EE room with
undecryptable history). Gate-green (tsc, eslint, prettier, 925 tests, build).

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

src/app/features/room-settings/ExportRoomHistory.tsx

@@ -92,6 +92,16 @@ export function ExportRoomHistory({ requestClose }: ExportRoomHistoryProps) {
           const evId = ev.getId();
           if (!evId || seen.has(evId)) continue;
           seen.add(evId);
+          // Advance the raw pagination boundary for EVERY event (any type,
+          // decrypted or not) — getTs() is unencrypted metadata. Gating this on
+          // a decrypted m.room.message let undecryptable/non-message old events
+          // stall oldestRawTs, so the fromTs break never fired → over-paginate
+          // and a false "truncated".
+          const ts = ev.getTs();
+          // Require a positive ts: an event with a bogus 0/negative
+          // origin_server_ts must not collapse the boundary and trigger an early
+          // break (silent under-pagination in the export).
+          if (ts > 0 && ts < oldestRawTs) oldestRawTs = ts;
           // Attempt decryption for events that haven't been decrypted yet
           // (paginateEventTimeline may fetch events before the SDK decrypts them)
           if (ev.isEncrypted() && !ev.getClearContent()) {
@@ -100,8 +110,6 @@ export function ExportRoomHistory({ requestClose }: ExportRoomHistoryProps) {
           }
           if (ev.getType() !== EventType.RoomMessage) continue;
           if (ev.isDecryptionFailure()) continue;
-          const ts = ev.getTs();
-          if (ts < oldestRawTs) oldestRawTs = ts;
           if (fromTs !== null && ts < fromTs) continue;
           if (toTs !== null && ts > toTs) continue;
           const content = ev.getContent();