build(solo): the 4.26" panel as a fourth L1 e-ink env

WioTrackerL1Eink426_solo_dual extends eink_solo like the 4.2" build and
sets only what differs: the panel, rotation, the 9x15 at 2x with Text and
Icon size, bulk writes at 8 MHz, 250 contacts and a 32-message queue.
Replaces the full copy of the flags in solo/wio-tracker-l1-gdeq0426/.
Docs: advert precision, text and icon size, the 4.26" in the feature matrix.

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

docs/solo/developer/feature-matrix.md

@@ -18,6 +18,7 @@ to some screens, adds or corrects its row here in the same commit.
 | **E-ink L** | Wio Tracker L1 e-ink, landscape | 250 × 122, 8 × 13 | Larger icons |
 | **E-ink P** | Wio Tracker L1 e-ink, portrait | 122 × 250, 6 × 9 | |
 | **E-ink 4.2"** | Wio Tracker L1 with the 4.2" panel (parked) | 400 × 300, 9 × 15 | Its own icon set |
+| **E-ink 4.26"** | Wio Tracker L1 with the 4.26" 800 × 480 panel (`WioTrackerL1Eink426_solo_dual`) | 400 × 240 at 2x, 9 × 15 | Text and icon size settings; "wide" like the 4.2", 16 lines |
 | **L2** | Wio Tracker L2 | 320 × 240 touch, ui-lvgl | |
 
 What decides it in ui-new (look for these when adding a screen):

docs/solo/settings.md

@@ -7,7 +7,7 @@ board supports are shown.
 
 | Section | What's there |
 | ------- | ------------ |
-| **Display** | Brightness, auto-off, wake on message, the message alert (banner, corner envelope or off), lock screen, the lock clock's look and the [PIN](./lock.md), battery as icon / % / volts, time zone, clock format and seconds; on e-ink also rotation and full refresh |
+| **Display** | Brightness, auto-off, wake on message, the message alert (banner, corner envelope or off), lock screen, the lock clock's look and the [PIN](./lock.md), battery as icon / % / volts, time zone, clock format and seconds; on e-ink also rotation and full refresh, and on a 4.26" panel the text and icon size |
 | **Sound** | Buzzer on / off / auto (quiet while the app is connected), volume, quiet hours, the melody for messages, channels and adverts |
 | **Home Pages** | Order of the home pages, and which are shown |
 | **Radio** | TX power, preset, frequency, SF / BW / CR, saved presets, Auto pwr, the scope list, then the advanced options (below) |
@@ -56,6 +56,10 @@ nodes aren't added until you make room.
   including the automatic ones. Off, nodes see your name but not where you
   are. Live sharing and `{loc}` in a message still send it, because you send
   those on purpose.
+- **Precision**: how exactly adverts give your position: **Exact**, or
+  rounded to a grid of about **100 m**, **500 m** or **1 km**. A fixed grid,
+  not random noise, so many adverts from one place can't be averaged back
+  to the exact spot.
 - **Position**: where your adverts say you are while the GPS is off. **Enter**
   to type it in (`50.06143, 19.93658`), take it from a waypoint, or clear it.
   With the GPS on, the row shows **GPS** and each fix replaces it; turning the