feat(scriptcompiler): add standalone SCB JSON converter

[bobtista]

• Closes Implement SCB to plain text to SCB compiler #288

Summary

• add ScriptCompiler tool to Core/Tools with bidirectional SCB JSON support
• use nlohmann-json via vcpkg and CMake
• support full roundtrip for scripts, groups, conditions, actions, params, preserving unknown chunks

Testing

• cmake --build build/unix --target core_scriptcompiler
• ./Core/Debug/scriptcompiler -in ~/Downloads/Scripts/SkirmishScripts.scb -out SkirmishScripts.json
• ./Core/Debug/scriptcompiler -in SkirmishScripts.json -out SkirmishScripts_roundtrip.scb
• Verified script/action/condition counts match between original and roundtrip outputs

[xezon]

The first observation is that the tool is decoupled from engine. Changing format in Engine will break the tool, unless changes are replicated to tool.

[bobtista]

The first observation is that the tool is decoupled from engine. Changing format in Engine will break the tool, unless changes are replicated to tool.

That's true. The point of that is so it's cross platform now. Some ideas:

• Extract the chunk structs + read/write helpers from the engine into a new library that’s platform-neutral
• Just have a process for updating the standalone tool whenever needed - how often will we need to do this really?
• Dual build: Add a Windows-only target and a macOS/Linux one, where only Mac users need to manually sync changes
• Scrap cross platform for now