Adds infrastructure to compile and run MicroPythonOS in the browser via Emscripten. Since lvgl_micropython/make.py has no webassembly target, the build uses MicroPython's upstream ports/webassembly Makefile directly (plain MicroPython + frozen Python files; LVGL canvas rendering is a follow-up once lvgl_micropython gains an Emscripten builder with -s USE_SDL=2).

C modules (c_mpos/micropython_wasm.mk)

• Includes only quirc (pure C, no system deps)
• Explicitly excludes: webcam (v4l2), adc_mic/pdm_mic (ESP-IDF), rvswd (ESP32 debugger), secp256k1-embedded-ecdh (possible x86 asm — pure-Python fallback already in lib/)

Python adaptation

• detect_board() in mpos/main.py returns "webassembly" when sys.platform == "webassembly", slotted between the linux/darwin and esp32 branches
• New mpos/board/webassembly.py: attempts SDL2 display/pointer init inside try/except (no-op without LVGL); skips audio, camera, and WiFi (WifiService already handles a missing network module gracefully)

Build script (scripts/build_mpos.sh wasm)

Sources emsdk, strips @micropython.viper (restored after build), compiles mpy-cross, then:

make -C ports/webassembly \
    USER_C_MODULES=".../c_mpos/micropython_wasm.mk" \
    FROZEN_MANIFEST=".../manifests/manifest.py"

Stages micropython.mjs, micropython.wasm, and html/index.html into lvgl_micropython/build/. The script documents the exact make.py invocation to switch to once lvgl_micropython gains Emscripten SDL2 support.

HTML shell (html/index.html)

• <canvas id="lvgl"> (320×240) for future LVGL SDL2 rendering via Emscripten's SDL2 port
• Terminal panel wired to Module.print / Module.printErr
• REPL input row calling mp_js_do_exec via ccall

CI (.github/workflows/wasm.yml)

Installs and caches emsdk, runs build_mpos.sh wasm, uploads .mjs, .wasm, and index.html as 7-day artifacts.