feat(panel): a status-only screen build for a board with no touch

[Zhongren233]

The panel feature drives a plain 4-wire SPI ST7789 (240x135, landscape) as a status screen: the build counter, the chip serial, whether USB is attached, and uptime — plus a PRESS THE KEY banner for as long as a user-presence wait is pending.

It is not the trusted display. Presence stays on the BOOTSEL button (or a PRESENCE_PIN), the banner renders nothing from the applet's Confirm, and shows_confirm keeps its false default, so CTAP semantics — including the authenticatorReset power-up window exemption — are a button key's. The banner is drawn from inside the wait rather than from the status task because the wait blocks the thread executor.

display cannot host this panel: 240x135 rather than 240x320, no touch controller, no PWM backlight, and its backlight pin is outside the display build's PWM allowlist. It is therefore a second screen feature, mutually exclusive with display, dep:-gated so a screenless key compiles none of it, and off the default image's dependency tree.

The reference board is ALIENTEK's RP2350A small-system board: CS=9, DC=8, and a backlight on GPIO25 that is active-LOW through a PNP high-side switch, over SPI1 with SCK/MOSI on the hard-wired GPIO10/11. Pins come from a board file's [panel] section and default to that board. Build with LED_KIND=none ... --features panel.

bcdDevice -> 0x09DB.

What

I found this development board “ALIENTEK RaspberryPi-RP2350A” on a Chinese online shopping site that costs only 24 RMB and comes with a screen.

and works well with standard firmware, but this borad dont have rgb light, so i think make use of this screen is a good idea.

How it was tested

• nix develop -c ./scripts/check.sh passes locally
• On hardware: board = …, what was exercised = …

Checklist

• Device behavior / image changed → config.device_release (bcdDevice) bumped by one (hex)
  in firmware/src/main.rs — host-only (CLI / docs / CI / build) does not (CONTRIBUTING.md)
• Fixes something a downgrade would reopen → flag whether the next release should advance the
  rollback epoch (docs/production.md, stage 3) — a seal-time --rollback call, not a code bump
• New or changed unsafe → justified in docs/unsafe.md
• User-visible behavior → the matching guide under docs/ updated
• New files carry the SPDX header (AGPL-3.0-only)
• Commit messages use the zone prefix style (fido:, piv:, rsk:, docs:, …)

[Zhongren233]

The code for this PR was written entirely by an agent, and I have no knowledge of the subject matter myself;
if somebody feel the quality is too poor, feel free to close this PR.

i already test on my borad.

6f26e99aa040be222abb1512917adab0.mp4

[Zhongren233]

It might be a duplicate of #123