feat(d211-linux): add ArtInChip D211 fbdev host and cross-build

[boa-z]

Adds a private d211-linux-dev target and native host for the ArtInChip D211DBV running Luban Linux 5.10 on RISC-V. Software rendering only — no EGL, GLES, DRM, or Wayland.

What landed

• hosts/d211-linux/ — fbdev presentation with FBIOGET_VSCREENINFO/FBIOGET_FSCREENINFO probing and a runtime channel-bitfield check; FBIOPAN_DISPLAY(yoffset=0) at startup so the host owns the scanned-out page; capability-probed evdev touch (EVIOCGNAME/EVIOCGBIT/EVIOCGABS, MT axes preferred); bounds hit resolved once at the down edge; damage-rect presentation scaled by raster density.
• tools/d211-linux-profile.ts — host ABI 11, platform: "linux", takeover form, logical viewport equal to the 800×480 panel at raster density 1, capabilities input.touch and text.glyphs.baked. Stays out of POCKET_TARGETS until the hardware acceptance receipt is complete.
• tools/d211-linux.ts + tools/d211-linux/build-runtime.sh — builds on the Ubuntu Luban builder with the Xuantie GCC wrapper and sysroot; final link through LLVM LLD from nightly-2026-07-02 because binutils 2.35 rejects modern RISC-V ELF attributes; JSON receipt records the commit, toolchain versions, sysroot, and digests.
• tools/d211-linux/remote-build.sh — macOS → builder sync, build, and artifact fetch in one command.
• apps/d211-demo/ — Hero wrapper on the wide-surface (largeLayout) variant.
• fix(ui-cabi) — declares the exported scaled raster entry points (ui_render*_scaled) in pocket_ui_cabi.h.
• test(d211-linux) — profile, host-probe, and build-bridge tests plus the demo admission-matrix entry.

Hardware validation

D211DBV, Luban Linux 5.10.44, build 472f7e072276bd38:

Measurement	Value
Boot (QuickJS init + app.js eval)	353 ms
Frame rate	59.9 fps
Damage	4,080 attempts, 0 failures, 2 full redraws
tick / render / present	avg 1.34 ms / 2.17 ms / 0.04 ms
Host RSS / MemAvailable	6.8 MB / ~17.8 MB, stable through touch input
Touch	33 clean down/up pairs at 800×480, one action per tap (Count: 34)

The captured 800×480 frame has no black pixels and the channel order matches the guest BGRA output. /tmp is a tmpfs on this board; an install under /tmp OOM-killed the host at 11 MB available, so deploy installs to /opt/pocketjs on the UBIFS rootfs, where the bundle stays reclaimable as page cache.

One correctness fix belongs to the host build: main.c was compiled with its fallback raster density while pocket_runtime.c received the plan value, so a density-1 plan rendered a scaled(2) surface. The define now reaches both translation units.

Reproduce

# Ubuntu builder with the Luban SDK built for d211:
bun tools/d211-linux.ts setup
bun tools/d211-linux.ts build
bun tools/d211-linux.ts doctor

# macOS with the D211 on ADB:
tools/d211-linux/remote-build.sh
bun tools/d211-linux.ts deploy
bun tools/d211-linux.ts stop-ui
bun tools/d211-linux.ts run

Build identity

Input	Pin
Rust	nightly-2026-07-02, target riscv64gc-unknown-linux-gnu (rustc 1.98.0-nightly)
GCC	Xuantie-900 V2.10.1, GCC 10.4.0 (Luban wrapper + sysroot)
Linker	LLD 22.1.8 from the same nightly (gcc-ld/ld.lld)
QuickJS	ba5bdd0dc013518768e76cd9e05cd30ed53dd35b (2026-06-04)
Executable	ec5ab5cadc5a87762188ac9be0128a17eeb7be5c0a3e02e9f664d1cd088d919a (2,818,360 bytes)
Core library	5df82ab904313f300ff5f5d8f05f3b11f9a501fc8b916ac1183e3544b1dabdda

Out of scope

Camera (TP9950), audio, CAN, and ADC are not touched. The test_lvgl autostart is still stopped manually before launch. d211-linux-dev promotes to a registered target after the remaining receipt items (multi-contact input, launch integration).

Baseline is current main; the handover plan's v0.10.1 suggestion predates v0.11.0.