- MainActivity: RECONNECT_DELAY_MS, POST_SETTINGS_RESCAN_MS, ON_RESUME_SCAN_DELAY_MS
- SettingsActivity: FLUSH_TIMEOUT_MS, READ_CHUNK_TIMEOUT_MS, CDC_CONTROL_TIMEOUT_MS
- UsbSerialTransport: CONTROL_LINE_TIMEOUT_MS
- UsbUtils: shared CDC request constants (REQUEST_TYPE, SET_LINE_CODING, SET_CONTROL_LINE_STATE, DTR, RTS)
Pure refactor — no behavior change. All literals replaced by named private const val in companion objects or shared via UsbUtils.
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