Selecting a Light or Dark theme makes AppCompatDelegate rewrite the
activity configuration to the forced night mode. isSystemInDarkTheme
reads that same configuration, so switching back to System kept showing
the previously forced theme.
Read the night mode from the application configuration instead, which
AppCompat leaves untouched and itself uses to expand
MODE_NIGHT_FOLLOW_SYSTEM. The activity configuration is still used as
the recomposition key so a system-wide theme change is picked up.
hayaksi1
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