feat: add play/stop controls for Studio simulation

[kevinswint]

Summary

Add tools for Claude to control Studio's play/simulation state:

• get_studio_state - Check current mode (edit/playtest/simulation)
• start_simulation - Start run mode (F8 - physics without player)
• start_playtest - Start play mode (F5 - with player character)
• stop_simulation / stop_playtest - Return to edit mode

⚠️ CRITICAL: Playtest Stop Limitation

stop_playtest cannot stop playtest mode (F5) from the plugin.

This is a fundamental Roblox limitation, not a bug:

• Playtest runs in a separate DataModel from the plugin
• RunService:Stop() from plugin context has no effect on playtest
• RunService:IsRunning() returns false from plugin context during playtest

What Works

Tool	Simulation (F8)	Playtest (F5)
start_simulation	✅ Works	N/A
start_playtest	N/A	✅ Works
stop_simulation	✅ Works	❌ No effect
stop_playtest	✅ Works	❌ No effect

How to Enable Programmatic Playtest Stop

To stop playtest programmatically, you must call StudioTestService:EndTest() from inside the running game. This requires adding a server script that can receive commands.

Option 1: Use run_server_code (requires MCPServerCodeRunner)

1. Add MCPServerCodeRunner.lua to your game's ServerScriptService
2. Enable HttpService in Game Settings > Security
3. Use the run_server_code tool:

run_server_code({ code = "game:GetService('StudioTestService'):EndTest('done')" })

Option 2: Manual Stop

Press F6 or click the Stop button in Studio.

Implementation Details

start_playtest

Uses StudioTestService:ExecutePlayModeAsync() wrapped in task.spawn() to avoid blocking the HTTP response. Returns immediately after dispatching the command.

start_simulation

Uses RunService:Run() with verification polling (works because simulation runs in same DataModel as plugin).

get_studio_state

Returns current mode using RunService:IsRunning() and RunService:IsRunMode():

• "edit" - Studio is in edit mode
• "playtest" - Play mode (F5) with player character
• "simulation" - Run mode (F8) without player

Note: During playtest, get_studio_state may incorrectly report "edit" due to DataModel isolation.

Files Changed

• plugin/src/Tools/StartPlaytest.luau - New tool
• plugin/src/Tools/Simulation.luau - start/stop simulation
• plugin/src/Tools/GetStudioState.luau - State detection
• src/rbx_studio_server.rs - Tool definitions

Test Plan

• start_playtest spawns player character
• start_simulation runs physics without player
• stop_simulation stops simulation mode
• stop_playtest stops simulation mode (not playtest - documented limitation)
• get_studio_state identifies edit and simulation modes

🤖 Generated with Claude Code

[kevinswint]

Fix for start_playtest not working

The original implementation called RunService:Run() which only starts simulation mode (F8) without a player character. This has been fixed to use the new StudioTestService:ExecutePlayModeAsync() API which starts actual playtest mode (F5) with a player character.

Changes Made:

1. StartPlaytest.luau: Uses StudioTestService:ExecutePlayModeAsync() wrapped in task.spawn() to avoid blocking the plugin (since the API yields until the test ends).

2. GetStudioState.luau: Now distinguishes between "playtest" and "simulation" modes using RunService:IsRunMode(). Returns additional fields: isRunMode and isPlaytest.

3. Simulation.luau: Clarified that start_simulation starts physics simulation without a player character.

Important Note:

During playtest, run_code commands will execute in the edit-mode context, not the playtest context. This is a Roblox Studio architecture limitation - plugins run in a separate DataModel from the playtest instance. Screenshot capture still works to observe playtest state.