Extract magic numbers to named constants

[tzermias]

Summary

This PR eliminates magic numbers throughout the codebase by extracting them into well-named constants, improving code readability and maintainability.

Constants Added

Protocol Constants:

• ✅ ProtocolPreamble1 = 0xf1 (Command message preamble byte 1)
• ✅ ProtocolPreamble2 = 0xf1 (Command message preamble byte 2)
• ✅ ProtocolResponse1 = 0xf2 (Response message preamble byte 1)
• ✅ ProtocolResponse2 = 0xf2 (Response message preamble byte 2)
• ✅ ProtocolTerminator = 0x7e (Message terminator)

Conversion Factors:

• ✅ HeightConversionFactor = 10 (Multiply height by 10 for protocol)

Memory Constants:

• ✅ MemoryPresetModulo = 0x24 (Modulo for memory preset calculation)

Timing Constants:

• ✅ PollingInterval = 200ms (Polling interval for height operations)
• ✅ SaveMemoryDelay = 200ms (Delay after saving memory preset)
• ✅ OperationTimeout = 60s (Default timeout for operations)
• ✅ InitializationDelay = 200ms (Delay during initialization)

Files Modified

pkg/jiecang/jiecang.go:

• Added all constant definitions
• Updated characteristicReceiver to use MemoryPresetModulo

pkg/jiecang/height.go:

• Updated GoToHeight to use HeightConversionFactor, ProtocolPreamble1/2, ProtocolTerminator, PollingInterval
• Updated readHeight to use HeightConversionFactor
• Updated readHeightRange to use HeightConversionFactor

pkg/jiecang/memory.go:

• Updated all GoToMemory functions to use PollingInterval
• Updated all SaveMemory functions to use SaveMemoryDelay
• Updated readMemoryPreset to use HeightConversionFactor

pkg/jiecang/common.go:

• Updated isValidData to use ProtocolResponse1/2, ProtocolTerminator

Benefits

• ✅ Readability: HeightConversionFactor is more descriptive than 10
• ✅ Maintainability: Change timing/conversion in one place
• ✅ Self-Documenting: Constants explain the purpose of values
• ✅ Consistency: Prevents using different hardcoded values
• ✅ Best Practices: Follows Go convention of named constants

Example

// Before (magic numbers)
data0 := byte((int(height) * 10) / 256)
ticker := time.NewTicker(200 * time.Millisecond)
if buf[0] != 0xf2 || buf[1] != 0xf2 {
    return false
}

// After (named constants)
data0 := byte((int(height) * HeightConversionFactor) / 256)
ticker := time.NewTicker(PollingInterval)
if buf[0] != ProtocolResponse1 || buf[1] != ProtocolResponse2 {
    return false
}

Breaking Changes

None - these are internal implementation details.

Test Results

make test   # ✅ PASS
make fmt    # ✅ PASS
make vet    # ✅ PASS

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