HTML <select> options can only store string values, so setting_options booleans
([True, False]) were serialised as 'true'/'false' strings and sent to the API.
Python's `x is True` check returned False for the string, making require_top_target
and deep_audio_verify permanently read as False regardless of what the user saved.
Fix JS: convert 'true'/'false' strings to real booleans before POSTing.
Fix Python: _to_bool() in quality_upgrade + inline coercion in scanner to handle
both existing string values in config and correct future booleans.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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