refactor(ui-core): UiCore becomes MyMesh's Listener for ui-new

ui-new hands MyMesh the UI Core (UITaskBase::meshListener()). The Core
applies the display filter, labels room posts, files history, keeps DM /
channel / room unread and the queue count, and reports incoming messages
and adverts as MessageArrived / AdvertHeard events. UITask now derives
UITaskBase + UiCoreHost: it answers "is this conversation on screen" and
keeps the selection after an insert, forwards not-yet-extracted parts
(room login / admin, bot device actions, removal cleanup, shutdown), and
turns events into alert / wake / sound, drained at the start and end of
its loop(). Mesh callbacks no longer touch the display or buzzer.

AbstractUITask is split into UITaskBase (lifecycle, link state, helpers)
and the Listener glue ui-orig / ui-tiny keep using unchanged. Screenshot
handler reaches ui_task directly instead of casting the Listener.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/development/ui-core.md

@@ -33,7 +33,7 @@ interleaved. Classified:
 
 **Engines — logic living inside `UITask.cpp` / `UITask.h`**
 - Unread tracking — DM unread table ✅ (`ui-core/DmUnreadTable.h`), room unread (still in `UITask`).
-- Notifications — `showAlert`, `notify`, `SoundNotifier`, LED (`userLedHandler`), wake-on-message (`checkDisplayOn`, auto-off).
+- Notifications ✅ split: the Core decides *what* happened (`MessageArrived` with kind / DM sender / channel slot, `AdvertHeard`); the frontend decides *how* to show it (`showAlert`, `SoundNotifier`, vibration, LED, wake-on-message) — those are platform services.
 - Live share ✅ `ui-core/LiveShareEngine.h` — session timer, movement/heartbeat gate, send + scope guard, peers' `LiveTrackStore` + expiry.
 - Locator ✅ `ui-core/LocatorEngine.h` — active target, geofence state machine, proximity beeper.
 - Trail ✅ `ui-core/TrailEngine.h` — store, sampling, auto-pause, low-battery auto-save.
@@ -70,11 +70,16 @@ fork's extensions (own-send mirroring, relay echoes, room login/admin replies,
 `[LOC]` shares, contact/channel removal, bot device actions,
 `requestShutdown`), each defaulting to a no-op.
 
-Today `AbstractUITask` is the Listener and carries the glue `MyMesh` used to
-run for the UI (display filter, room-post labelling, notifications). In the
-target design `UiCore` becomes the Listener instead: it updates models/engines
-and emits events, and the frontends no longer implement it at all. This is the
-single point that makes both frontends receive identical behaviour.
+For `ui-new`, `UiCore` is the Listener (`UITaskBase::meshListener()` hands it
+to `MyMesh::setListener()`): it applies the display filter, labels room posts,
+files history, keeps unread counters, runs the engines and emits events. The
+frontend implements `UiCoreHost` (`ui-core/UiCoreHost.h`) for what the Core
+still asks of it synchronously: "is this conversation on screen", "keep the
+selection after an insert", and forwarding for not-yet-extracted parts (room
+login / admin sessions, bot device actions, prefs cleanup on contact/channel
+removal, shutdown). `ui-orig` / `ui-tiny` keep `AbstractUITask`, which is
+`UITaskBase` + the Listener glue, unchanged. This is the single point that
+makes both frontends receive identical behaviour.
 
 ### 2. Engines
 
@@ -151,8 +156,8 @@ checked in the sim plus on L1 hardware before the next one.
 
 0. **Listener boundary** ✅ (upstream `MyMesh::Listener` ported; `MyMesh` has no UI calls left).
 1. **Skeleton** ✅. `examples/companion_radio/ui-core/` with `UiCore.h` (facade), `MessageHistory.h`, `DmUnreadTable.h`. Header-only for now, reached from `ui-new/UITask.cpp` by relative include, so none of the 66 variant `platformio.ini` files that build `ui-new` change. `UITask` heap-allocates one `UiCore` in `begin()` (before the screens, as `MessagesScreen` used to own the history on the heap); `MessagesScreen` binds to `core().history` by reference. When the Core grows real `.cpp` files, compile them through a unity `.cpp` inside each frontend directory.
-2. **Engines, one per commit.** Clock tools ✅ (also introduced `ui-core/UiEvents.h`, the Core → frontend event queue; `UITask::tickCore()` runs `UiCore::loop()` and drains it) → ping ✅ → course-over-ground ✅ → live share ✅ → locator ✅ → trail ✅ → notifications. `UITask` shrinks to screen management + drawing.
-3. **Flip the interface.** `UiCore` implements `AbstractUITask`; `ui-new`'s `UITask` becomes a frontend fed by events.
+2. **Engines, one per commit.** Clock tools ✅ (also introduced `ui-core/UiEvents.h`, the Core → frontend event queue; `UITask::tickCore()` runs `UiCore::loop()` and drains it) → ping ✅ → course-over-ground ✅ → live share ✅ → locator ✅ → trail ✅ → notifications ✅ (with step 3). `UITask` shrinks to screen management + drawing.
+3. **Flip the interface** ✅. `UiCore` is `MyMesh::Listener`; `ui-new`'s `UITask` derives `UITaskBase` + `UiCoreHost` and is fed by events, drained at the start (mesh-originated) and end (engines) of its `loop()`. Mesh callbacks no longer touch the display or buzzer directly.
 4. **Settings schema.** Convert `SettingsScreen` section by section.
 5. **`ui-lvgl` skeleton** for L2 + sim target: boot, home, message list/conversation, keyboard. Then screens by priority.
 6. Contacts/Nearby, Admin, Bot logic extraction as the LVGL screens for them are built.