Add GameMaker Studio 2024.13 engine reference and agent configurations

[fikrydev]

Summary

Adds GameMaker Studio 2024.13 (IDE 193 / Runtime 242) as a fully supported
engine alongside Godot, Unity, and Unreal Engine. Coverage is end-to-end:
reference docs, specialist agents, project config, and every cross-engine list
in the repository.

What changed

Engine reference docs (docs/engine-reference/gamemaker/)

• VERSION.md — version pin for GMS 2024.13
• breaking-changes.md — function inheritance (self. prefix requirement),
  typed handle refs replacing numeric asset IDs, noone return type change,
  deprecated OS constants
• deprecated-apis.md — deprecated patterns and changed return types
• current-best-practices.md — UI Layers, FlexPanel, collision API, new 2024.13 additions
• modules/ — five reference modules: gml-language, rooms-layers, ui-draw-gui,
  audio, assets

Specialist agents (.opencode/agents/)

Six new agents with full documentation and cross-referenced coordination:

• gamemaker-specialist — lead: GML patterns, room/object architecture, sequences
• gamemaker-gml-specialist — NEW: hands-on GML code writing, review, language patterns, style guide
• gamemaker-performance-specialist — draw calls, object pooling, surface batching, profiling
• gamemaker-shader-specialist — GLSL ES shaders, shader passes, post-processing
• gamemaker-assets-specialist — sprites, audio, asset groups, runtime loading
• gamemaker-ui-specialist — UI Layers, FlexPanel, draw_gui events
• gamemaker-networking-specialist — rollback netcode, async, buffer management
  New in gamemaker-gml-specialist:
• Comprehensive GML style guide (naming, comments, formatting)
• GML language patterns (structs, state machines, exceptions, coroutines, save/load)
• Complete .yy file event number tables (eventtype + enumb for all events)
• Common GML coding pitfalls with explanations
• Recommended community libraries (Coroutines, SNAP, Exception.gml, etc.)
• Full reference documentation (~70 URLs organized by category):
  • Official GML manual (LTS + Monthly versions)
  • Style guides & naming conventions (GitHub, gamedev.wtf, forum threads)
  • Event number mapping (Stack Overflow, forum)
  • Patterns & architecture articles (GML 2.3, save/load, state machines)
  • Video references & performance guides
    Updated in existing agents:
• All five sub-specialists now reference gamemaker-gml-specialist in their peer coordination sections
• gamemaker-specialist simplified to architecture-only; delegates GML code to gamemaker-gml-specialist

Project-wide updates

• OPENCODE.md — imports GameMaker VERSION.md alongside Godot/Unity
• .opencode/opencode.json — all 7 agents registered (agent count 48 → 55)
• README.md — agent count updated; GameMaker listed in studio hierarchy tier
• docs/WORKFLOW-GUIDE.md — engine hint text, subsystem examples, quick-reference table
• .opencode/docs/agent-roster.md — Engine Leads table + GameMaker Sub-Specialists section
• .opencode/docs/agent-coordination-map.md — GameMaker branch in engine specialist tree
• .opencode/docs/quick-start.md — task-to-agent routing (all 7 GameMaker agents)
• .opencode/skills/setup-engine/SKILL.md — decision matrix, naming conventions, template
• .opencode/skills/brainstorm/SKILL.md — engine recommendation options
• .opencode/docs/templates/game-concept.md and pitch-document.md — engine choice field
• .opencode/rules/shader-code.md — GML shader grouping note
• docs/engine-reference/README.md — GameMaker in overview section
• docs/COLLABORATIVE-DESIGN-PRINCIPLE.md — agent count updated

Scope

Approximately 45 files changed, 3300+ insertions, 100+ deletions.
Engine-specific files for Godot, Unity, and Unreal are untouched.

Key highlights

1. Naming convention: gamemaker-gml-specialist (not just gml-specialist) to avoid ambiguity with other engines' language specialists (GDScript, C#/MonoBehaviour, GML, etc.)
2. Clear separation of concerns:
   • gamemaker-specialist = engine architecture, objects, rooms, events, platform builds
   • gamemaker-gml-specialist = language-level coding, style, patterns, API usage
3. Comprehensive reference: All GML documentation (official + community) now lives in one agent, making it the canonical knowledge base for GML coding tasks
4. Agent hierarchy: 1 lead + 6 sub-specialists, fully integrated into the studio's cross-engine agent coordination system