Fix all compilation warnings (CS9107, CS8600, CS8604, CS8618, CS0168, CS0169, CS0649)

- Fix CS9107: Replace lowercase primary constructor parameter refs with
  PascalCase base class properties in 90+ StructuredComponent files
- Fix CS8618: Add null! initializers for late-initialized properties
- Fix CS8600: Use nullable out parameters in World.cs, ChatParser.cs
- Fix CS8604: Add null guard in Compiler.cs, fix null-conditional in McClient.cs
- Fix CS0168: Replace unused variable with discard in DataTypes.cs
- Fix CS0169: Remove unused motionY field from McClient.cs
- Fix CS0649: Remove never-assigned steps field, simplify ClientIsMoving()
- Initialize client/handler with null! to avoid CS8618 cascade

Co-authored-by: milutinke <441903+milutinke@users.noreply.github.com>
Agent-Logs-Url: https://github.com/milutinke/Minecraft-Console-Client/sessions/7fcee1b2-21e2-4457-b01b-5e0a1f07752f

MinecraftClient/Scripting/DynamicRun/Builder/Compiler.cs

@@ -82,6 +82,8 @@ namespace MinecraftClient.Scripting.DynamicRun.Builder
             {
                 // Create a temporary file to copy the executable to.
                 var executablePath = Environment.ProcessPath;
+                if (executablePath is null)
+                    throw new InvalidOperationException("Cannot determine the process path for self-contained scripting extraction.");
                 var tempPath = Path.Combine(Path.GetTempPath(), "mcc-scripting");
                 Directory.CreateDirectory(tempPath);