refactor(netpacket): Simplify initialization of net packet field types

[xezon]

Merge with Rebase

• Follow up for refactor(netpacket): Simplify packet serialization code by using packed structs #1680

This change has 2 commits:

1. Streamlines the order of the net packet fields for easier reading

2. Simplifies the initialization of the net packet field types by using constructor initialization and the placement new operator

TODO

• Add pull id's to commit titles
• Fix undefined behavior

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Greptile Overview

Greptile Summary

Simplified network packet field initialization by adding constructors to field structs that automatically set field type identifiers, eliminating repetitive manual assignments across 23 packet serialization functions.

Key Changes:

• Reordered NetPacketFieldTypes constants to match the order in which fields appear in packet structs for easier reading
• Renamed header field to fieldType in all packet field structs for clearer semantics
• Added constructors to initialize fieldType automatically using member initializer lists
• Replaced reinterpret_cast with placement new syntax to leverage constructors
• Removed 69 lines of manual field type assignments (e.g., packet->commandType.header = NetPacketFieldTypes::CommandType)

Technical Correctness:
The placement new approach is safe here because all structs use #pragma pack(1) for 1-byte alignment, ensuring deterministic memory layout without padding. The constructors initialize only the fieldType member via initializer lists before the constructor body runs, leaving other fields for explicit assignment as intended.

Confidence Score: 5/5

• This PR is safe to merge with no concerns
• The refactoring is well-designed and mechanically correct. The use of placement new with constructors is safer than the previous reinterpret_cast approach, as it properly constructs objects. The 1-byte packing ensures memory layout compatibility. The change reduces code duplication and eliminates a common source of bugs (forgetting to initialize field types). All 23 functions follow the same pattern consistently.
• No files require special attention

Important Files Changed

Filename	Overview
Core/GameEngine/Include/GameNetwork/NetPacketStructs.h	Reordered field type constants to match struct usage order and renamed header to fieldType in all structs; added constructors to initialize field types
Core/GameEngine/Source/GameNetwork/NetPacket.cpp	Replaced reinterpret_cast with placement new to leverage struct constructors for automatic field type initialization, removing manual header assignments

Sequence Diagram

sequenceDiagram
    participant Caller
    participant NetPacket
    participant Buffer as UnsignedByte* buffer
    participant Struct as NetPacket*Command

    Caller->>NetPacket: FillBufferWithXXXCommand(buffer, msg)
    Note over NetPacket: Extract command data from msg
    NetPacket->>Buffer: new (buffer) NetPacketXXXCommand
    Note over Buffer,Struct: Placement new constructs object at buffer location
    Struct-->>NetPacket: packet pointer
    Note over Struct: Constructor auto-initializes fieldType
    NetPacket->>Struct: packet->commandType.commandType = value
    NetPacket->>Struct: packet->frame.frame = value
    NetPacket->>Struct: packet->relay.relay = value
    NetPacket->>Struct: packet->playerId.playerId = value
    Note over Struct: Other fields explicitly assigned
    NetPacket-->>Caller: Buffer filled with serialized packet

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_{Last reviewed commit: a0b6d3f}

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_{2 files reviewed, 1 comment}

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[Mauller]

Looks good, just needs that followup

[xezon]

@greptileai