docs: version this cycle's release notes as v1.25, flag new boards experimental

Names the upcoming release and marks the Cardputer ADV / T-Echo Lite
KeyShield board support as experimental, since it's new enough not to
have had much real-world use yet.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

release-notes.md

@@ -1,8 +1,8 @@
-## Unreleased
+## MeshCore Solo Companion Firmware v1.25
 
 ### What's new
 
-- **Two new boards with a keyboard built in: M5Stack Cardputer ADV and LilyGO T-Echo Lite + KeyShield.** Both drive the solo UI from a real keypad, so neither needs a CardKB or a wired joystick to be a complete standalone device. The **Cardputer ADV** (ESP32-S3, ST7789 TFT, built-in QWERTY) is supported across the full env range — companion over BLE or USB, solo (`M5Stack_Cardputer_ADV_companion_solo_dual`), repeater, ESP-NOW repeater bridge, room server, terminal chat and KISS modem — and detects at boot whether its LoRa module is fitted, via the PI4IOE5V6408 IO-expander. The **KeyShield** is an add-on for the LilyGO T-Echo Lite (whose base variant arrived from upstream), giving it a T9 keypad and a controllable backlight, with its own solo build (`LilyGo_T-Echo-Lite_keyshield_companion_solo_dual`). Bringing the KeyShield variant in also caught four issues in that base variant — swapped GPS RX/TX pins, the wrong TCXO voltage, an unused TX LED, and a missing e-ink panel include — and the KeyShield solo build itself picked up the `-Os` size optimisation every other nRF52 solo build already had (it had been missed), taking flash use from 90.7% down to 61.4%. Both keypads are TCA8418-based and share one polling path, independent of the CardKB support — a board can have either, or neither. The Cardputer's ST7789 driver also gained the misc-fixed 6×9 font (full Latin, Greek and Cyrillic), so its on-screen keyboard types every alphabet the other solo boards can rather than falling back to transliteration.
+- **Experimental: two new boards with a keyboard built in — M5Stack Cardputer ADV and LilyGO T-Echo Lite + KeyShield.** Newly-added board support, so treat both as experimental until they've had more hands on them. Both drive the solo UI from a real keypad, so neither needs a CardKB or a wired joystick to be a complete standalone device. The **Cardputer ADV** (ESP32-S3, ST7789 TFT, built-in QWERTY) is supported across the full env range — companion over BLE or USB, solo (`M5Stack_Cardputer_ADV_companion_solo_dual`), repeater, ESP-NOW repeater bridge, room server, terminal chat and KISS modem — and detects at boot whether its LoRa module is fitted, via the PI4IOE5V6408 IO-expander. The **KeyShield** is an add-on for the LilyGO T-Echo Lite (whose base variant arrived from upstream), giving it a T9 keypad and a controllable backlight, with its own solo build (`LilyGo_T-Echo-Lite_keyshield_companion_solo_dual`). Bringing the KeyShield variant in also caught four issues in that base variant — swapped GPS RX/TX pins, the wrong TCXO voltage, an unused TX LED, and a missing e-ink panel include — and the KeyShield solo build itself picked up the `-Os` size optimisation every other nRF52 solo build already had (it had been missed), taking flash use from 90.7% down to 61.4%. Both keypads are TCA8418-based and share one polling path, independent of the CardKB support — a board can have either, or neither. The Cardputer's ST7789 driver also gained the misc-fixed 6×9 font (full Latin, Greek and Cyrillic), so its on-screen keyboard types every alphabet the other solo boards can rather than falling back to transliteration.
 - **Solo builds for Heltec V3 and V4** (`Heltec_v3_companion_solo_dual`, `heltec_v4_companion_solo_dual`) — the full standalone on-device UI instead of a screen that only mirrors the phone app, with dual transport so the companion app can attach over BLE or USB serial (BLE wins while both are live), same as the Wio Tracker L1 solo builds. Dual transport had only ever been built for nRF52, so ESP32 got its own `DualSerialInterface` to match. Both boards ship with a single button, which the solo UI can't be driven from, so each env enables both supported input devices with default pins picked from what that board leaves free: a **CardKB** on a second I2C bus (pair it with Ext. KB = Compact and no joystick is needed at all) and a **wired joystick** (four direction pins plus a Back button, wired straight to GND — the firmware enables the internal pull-ups). Either is enough on its own, and pins with nothing attached read as not-pressed, so the unused half costs nothing. The env comments list which GPIOs each board has already claimed, for anyone wiring theirs differently. The release job initially only attached `*.uf2`/`*.zip` (which covered every solo board back when they were all nRF52), so these two boards' `.bin` images would have shipped nowhere; releases now also carry a `-merged.bin` (bootloader + partition table + app, flashed at `0x0`) per ESP32 board.
 - **Screenshot support on the Heltec V3/V4 solo builds.** `ENABLE_SCREENSHOT` was set on every other solo env but these two, so [Solo Tools](https://marekzegare4.github.io/Solo-tools/) couldn't capture their display. Now consistent across all seven solo builds.
 - **GPS duty-cycling — Settings › System › "GPS pwr"** (boards with GPS). Off by default (today's always-on behaviour); pick 1/5/15/30 min or 1 h and GPS sleeps for that long between fixes instead of running continuously — each wake waits for a fix, capped at 60s, before going back to sleep. Automatically stays continuously on regardless of this setting whenever something actually needs a live position: an active Trail recording, Map › Live share, an armed Locator, the Compass / Nearby navigate view, or an in-flight `!gps fix` request (so its own up-to-300s acquire window isn't cut short by the 60s cap) — so none of those features degrade, only the idle time between them gets cheaper. Manually turning GPS on or off while duty-cycling is running no longer confuses the scheduler's own sleep/wake timer into immediately reversing the change. The GPS status icon blinks while napping.