feat: Enable Farmer bot support for legacy 1.8 to 1.12.2

[Copilot]

Farmer was blocked on 1.8-1.12.2 by bot-specific gaps, not by missing core inventory support. This updates the legacy crop and placement paths so Farmer can run on pre-flattening versions where MCC already supports terrain and inventory handling.

• Farmer legacy compatibility

  • lower the Farmer startup gate from < 1.13 to < 1.8
  • add pre-1.13 crop maturity checks using legacy block ID + metadata
  • handle legacy melon/pumpkin stems by treating max-age stems or stems adjacent to fruit as harvestable

• Legacy block mapping

  • add missing 1.12.2 beetroot mapping in Palette112 so world scans can discover beetroot crops

• Legacy protocol fix

  • fix the < 1.9 PlayerBlockPlacement path to actually send the packet after encoding it
  • this unblocks planting and bonemeal interactions on 1.8.x

• Docs and messaging

  • update the Farmer unsupported-version message to reflect the real floor of 1.8
  • remove stale docs claiming inventory handling is unsupported on 1.8-1.9
  • tighten the Farmer docs to describe it as experimental, especially on legacy versions

Example of the legacy maturity path added for pre-1.13 crops:

private bool IsLegacyCropFullyGrown(Block block, CropType cropType, Location? location)
{
    return cropType switch
    {
        CropType.Beetroot => block.BlockId == 207 && block.BlockMeta >= 3,
        CropType.Carrot => block.BlockId == 141 && block.BlockMeta >= 7,
        CropType.Melon => block.BlockId == 105
            && (block.BlockMeta >= 7 || HasAdjacentBlock(location, Material.Melon)),
        CropType.NetherWart => block.BlockId == 115 && block.BlockMeta >= 3,
        CropType.Pumpkin => block.BlockId == 104
            && (block.BlockMeta >= 7 || HasAdjacentBlock(location, Material.Pumpkin)),
        CropType.Potato => block.BlockId == 142 && block.BlockMeta >= 7,
        CropType.Wheat => block.BlockId == 59 && block.BlockMeta >= 7,
        _ => false
    };
}

[milutinke]

Tested it a bit, I'll merge it after the movement refactoring and after I test it a bit more.