Fix hw---gdk simulator crash: add readP0Adc simulator fallback

[GarbhitSh]

Summary

Follow-up to #7600. Selecting Game Designer's Kit (hw---gdk) and running a project in the simulator crashes a couple of seconds after start with:

Cannot read properties of undefined (reading 'readP0Adc')

This PR adds a simulator fallback for the gdk.readP0Adc() shim so the board works in the simulator. No device behavior changes.

Root cause

readP0Adc() is a native SAADC shim implemented only in C++ (analog.cpp) and exposed via a declaration-only shims.d.ts:

//% shim=gdk::readP0Adc
function readP0Adc(): int32;

The battery-low monitor in batteryled.ts calls it from a background loop:

control.runInBackground(function () {
    pause(STARTUP_DELAY_MS);
    updateLed();
    while (true) {
        pause(REFRESH_MS);
        updateLed();       // -> readAdcAveraged() -> readP0Adc()
    }
});

Because the shim has no simulator implementation, gdk.readP0Adc is undefined in the browser, and the background loop throws the error above. This affects every project built for hw---gdk in the simulator, regardless of user code.

Fix

Give the shim a TypeScript fallback body, mirroring the existing pattern in libs/storage (storage::init), which uses a C++ shim with a TS body and no shims.d.ts:

• Add libs/hw---gdk/analog.ts with //% shim=gdk::readP0Adc and a fallback body returning a full-battery reading (1023).
• Remove the declaration-only libs/hw---gdk/shims.d.ts (it would otherwise duplicate the declaration).
• Update libs/hw---gdk/pxt.json files accordingly.

On micro:bit V2 the native C++ SAADC read is still used and is unchanged; in the simulator the fallback runs, so updateLed() sees a healthy value (1023 > 700), the low-battery LED stays off, and nothing crashes.

namespace gdk {
    //% shim=gdk::readP0Adc
    export function readP0Adc(): number {
        return 1023;
    }
}

Test plan

• Simulator with hw---gdk selected: the readP0Adc runtime error no longer occurs; battery LED indicator stays off
• pxt.json parses; git diff --check clean
• micro:bit V2 hardware: battery reading / low-battery LED behavior unchanged (C++ path untouched)

Notes

• Device (C++) code path is untouched; this is additive for the simulator only.
• Pattern reference: libs/storage/storage.ts + libs/storage/storage.cpp.

[Copilot]

Pull request overview

Fixes a simulator-only crash for the hw---gdk hardware variant by providing a TypeScript fallback implementation for the native-only gdk.readP0Adc() SAADC shim, ensuring projects can run in the browser simulator without undefined shim errors while leaving device (C++) behavior unchanged.

Changes:

• Added libs/hw---gdk/analog.ts implementing gdk.readP0Adc() with a simulator fallback body returning 1023, while still mapping to the native shim via //% shim=gdk::readP0Adc.
• Removed the declaration-only libs/hw---gdk/shims.d.ts to avoid duplicate/conflicting declarations now that the shim is defined in TypeScript.
• Updated libs/hw---gdk/pxt.json to include the new analog.ts and drop shims.d.ts.

Show a summary per file

File	Description
libs/hw---gdk/shims.d.ts	Removes the declaration-only shim definition so it doesn’t conflict with the new TS-backed shim implementation.
libs/hw---gdk/pxt.json	Registers analog.ts in the package and removes shims.d.ts from the build inputs.
libs/hw---gdk/analog.ts	Adds a TS shim definition with a simulator fallback body to prevent readP0Adc from being undefined in the browser.

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