feat(display): add R8 portrait observer layouts

test/README.md

@@ -30,6 +30,7 @@ does not reflect the GoogleTest count — run the built binary directly
 | `test_mqtt_topic_router` | `src/helpers/MQTTTopicRouter.h` | complete preset/custom topic-routing contract; MeshRank all types except raw; required identifiers; invalid inputs/slots; exact buffer boundaries |
 | `test_mqtt_connection_policy` | `src/helpers/MQTTConnectionPolicy.h` | reconnect guard/backoff/stagger and breaker transitions; stable reset; JWT lifetime/renewal policy; exact timing boundaries and 32-bit `millis()` rollover; WiFi current-outage start sticky across STA reconnect attempts |
 | `test_alert_fault_policy` | `src/helpers/AlertFaultPolicy.h` | WiFi/MQTT fault edge detector; `OutageSnapshot` (down / started_ms / initiating reason) fed to tick and `formatWifiAlert`; reason-8 reconnects change neither duration nor initiating reason; flap between status polls; down at `millis()==0`; packed 64-bit cross-task word; rate-limit floor and first-fire; 5 s poll cadence and `millis()` rollover |
+| `test_display_viewport` | `src/helpers/ui/DisplayViewport.h`, `src/helpers/ui/DisplayFrameSignature.h` | logical-to-physical portrait mapping; fractional span coverage; fitted-width conversion; preferred/fallback text scaling; stable visible-frame change detection |
 | `test_mqtt_packet_queue_policy` | `src/helpers/MQTTPacketQueuePolicy.h` | queue-full eviction; stale-disconnect flush; adaptive drain limits; bounded QoS0 retries; exact timing boundaries and 32-bit `millis()` rollover |
 | `test_mqtt_packet_filter` | `src/helpers/MQTTPacketFilter.h` | per-slot 0-15 allowlist parsing/formatting, numeric and named spellings; exact bounds; membership; candidate/eligible split and retry-completion policy; pre-queue union gate; default-mask detection |
 | `test_mqtt_runtime_buffer_lifecycle` | `src/helpers/MQTTRuntimeBufferLifecycle.h` | idempotent allocation/release; partial-allocation degradation; retry of only missing buffers |