sentry-api-schema /events/ dataset enum is incomplete — blocks SDK adoption

The OpenAPI spec for GET /api/0/organizations/{org}/events/ had two blockers preventing CLI migration to the generated SDK: (1) dataset enum only listed ['logs', 'profile_functions', 'spans', 'uptime_results'] — missing 'transactions', 'errors', 'discover'; (2) cursor parameter was not declared at all, despite 3 of 4 call sites using it for pagination. Both fixed in sentry PR #114787: widen VisibilityParams.DATASET enum in parameters.py, add CursorQueryParam to @extend_schema parameters in organization_events.py. Pattern: paginated endpoints declare cursor via CursorQueryParam serializer class (42 endpoints use this pattern). After these fixes, PR #69's wrapper generator auto-detects the endpoint and emits typed pagination wrappers, unblocking all 4 raw apiRequestToRegion call sites.