fix(power): correct charge/power detection preprocessor bugs (#10906)

* fix(power): check EXT_CHRG_DETECT with defined(), not truthiness

#elif EXT_CHRG_DETECT tests the macro's numeric value rather than
whether it's defined. Every existing board happens to assign it to a
nonzero pin, so this never misfired, but a board using pin 0 (e.g.
PA0 on STM32) would silently skip this branch even though the pin is
defined and configured.

Assisted-by: Claude Sonnet 5 <noreply@anthropic.com>
Signed-off-by: Andrew Yong <me@ndoo.sg>

* fix(power): consider EXT_CHRG_DETECT in isVbusIn()

isVbusIn() used EXT_PWR_DETECT alone. On boards where that pin is a
charge-complete/standby signal rather than a continuous power-present
signal, isVbusIn() reports false for the entire duration of an active
charge. If EXT_CHRG_DETECT is also defined, OR it in: charging can
only happen when power is present, so this only adds correct true
results and is a no-op for boards where EXT_PWR_DETECT already means
"power present" continuously.

Assisted-by: Claude Sonnet 5 <noreply@anthropic.com>
Signed-off-by: Andrew Yong <me@ndoo.sg>

---------

Signed-off-by: Andrew Yong <me@ndoo.sg>
Co-authored-by: Ben Meadors <benmmeadors@gmail.com>

src/Power.cpp

@@ -551,7 +551,16 @@ class AnalogBatteryLevel : public HasBatteryLevel
             return sgm41562->isInputPowerGood();
 #endif
 #ifdef EXT_PWR_DETECT
-        return digitalRead(EXT_PWR_DETECT) == EXT_PWR_DETECT_VALUE;
+        if (digitalRead(EXT_PWR_DETECT) == EXT_PWR_DETECT_VALUE)
+            return true;
+#ifdef EXT_CHRG_DETECT
+        // EXT_PWR_DETECT alone may not catch active charging (e.g. a charge-complete
+        // pin that only asserts once the battery is full) - CHRG being active implies
+        // power is present regardless.
+        return digitalRead(EXT_CHRG_DETECT) == EXT_CHRG_DETECT_VALUE;
+#else
+        return false;
+#endif
 
 // technically speaking this should work for all(?) NRF52 boards
 // but needs testing across multiple devices. NRF52 USB would not even work if
@@ -577,7 +586,7 @@ class AnalogBatteryLevel : public HasBatteryLevel
 #endif
 #if defined(ELECROW_ThinkNode_M6)
         return digitalRead(EXT_CHRG_DETECT) == EXT_CHRG_DETECT_VALUE || isVbusIn();
-#elif EXT_CHRG_DETECT
+#elif defined(EXT_CHRG_DETECT)
         return digitalRead(EXT_CHRG_DETECT) == EXT_CHRG_DETECT_VALUE;
 #elif defined(BATTERY_CHARGING_INV)
         return !digitalRead(BATTERY_CHARGING_INV);