docs: messages kept on the L1's flash (Keep messages, Delete after, Delete history), Powered off and the power switch on e-ink

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

docs/solo/developer/ui-core.md

@@ -29,6 +29,7 @@ interleaved. Classified:
 
 **Models — already UI-free, move as-is**
 - `MessageHistory.h` — channel (48) / DM (32) rings, unread counters + overflow flags. ✅ moved to `ui-core/`.
+- `HistoryLog.h` (`HIST_FLASH`, the L1s) — the rings' `HistArchive` on the QSPI flash: two append-only logs, one directory per segment because LittleFS 1.x erases a directory's two fixed blocks on every commit. Older messages reach `MessageHistory::older` a page at a time, since ui-new measures its whole list every frame.
 - `Trail.h` / `TrailStore`, `ScopeList.h`. Waypoints ✅ `ui-core/WaypointModel.h` (store + `/waypoints` persistence + "delete clears the Locator target"; ui-new's `UITask::waypoints()` forwards to it).
 
 **Engines — logic living inside `UITask.cpp` / `UITask.h`**

docs/solo/hardware.md

@@ -96,6 +96,10 @@ The e-ink screens show more than the OLED, the portrait one most:
   arrows in the node list;
 - under a saved trail (portrait), its map and elevation profile.
 
+Hibernating leaves **Powered off** on the screen, and it stays there even if
+you then use the power switch. The switch alone cuts the board with no warning,
+so the screen goes grey or dark soon after: hibernate first to keep it clean.
+
 Settings › Display has a few settings of its own:
 
 - **Rotation** turns the screen upside down; the joystick turns with it.

docs/solo/messages.md

@@ -57,6 +57,18 @@ haven't read, its unread count gets a **+** (for example `48+`).
 > messages each, Settings › Storage). The history survives a reboot and
 > scrolls back through everything on the card.
 
+> [!NOTE]
+> **Wio Tracker L1:** with **Keep messages** on (Settings › Messages, off by
+> default) messages are also saved on the flash, 500, 1000 or 2500 in total:
+> two thirds for channels, one third for direct messages and rooms. The newest
+> come back after a power-off. Scrolling past the oldest message of a
+> conversation goes on to the saved ones, twelve at a time; **Back** returns
+> to the newest.
+>
+> Messages are saved within a minute of arriving, or sooner in a burst. The
+> power switch cuts the power at once, so it can lose that last minute;
+> hibernating and the low-battery shutdown save first.
+
 ## Writing
 
 Open a conversation and choose **+ Send** (or Enter at the bottom of the

docs/solo/settings.md

@@ -15,7 +15,7 @@ board supports are shown.
 | **Keyboard** | ABC or T9 layout, the two scripts, CardKB mode |
 | **Contacts** | Show all or favourites only (DMs, channels, rooms), favourites on top, the order of the channel list, contact expiry and prune, which heard nodes are added |
 | **Privacy** | Whether your adverts carry your position and which position, who may ask for your status, location and sensor readings, the Bluetooth PIN |
-| **Messages** | Automatic resend of direct messages, the ten quick messages |
+| **Messages** | Automatic resend of direct messages, on the Wio Tracker L1 the messages kept on flash (below), the ten quick messages |
 
 A few notes:
 
@@ -36,6 +36,16 @@ A few notes:
   doesn't follow the usual LiPo curve: **Left / Right** move a point by
   10 mV, **Reset** goes back to LiPo. The current voltage is shown, so a point
   can be set against what the battery reads.
+- **Keep messages** (Wio Tracker L1) saves messages on the flash, across a
+  power-off and past what fits in memory (see
+  [How much is kept](./messages.md#how-much-is-kept)): **Off**, 500, 1000 or
+  2500 in total. When the limit is reached the oldest go, in batches. Setting
+  it to Off deletes what was saved.
+- **Delete after** (Wio Tracker L1) removes saved messages older than 7, 30 or
+  90 days, or **Never**. They go in batches too, so some stay a little longer,
+  and nothing goes while the clock isn't set.
+- **Delete history** (Wio Tracker L1) deletes every message, saved and in
+  memory, after asking.
 - **Factory reset** erases contacts, channels, messages, settings and the
   node's keys, then restarts as a new node. It asks twice. On the Wio Tracker
   L2 the SD card is left as it is.