Fix: prevent Studio freeze when clicking Test button

[TonyD365]

Summary

Fix Studio freeze issue when clicking the Test button in Roblox Studio.

Root Cause

The start_test handler called RunService:Run() synchronously, which is a blocking operation. This prevented the WebSocket message handler from returning, causing Studio to freeze when the desktop app sent a start_test command.

Solution

Wrapped RunService:Run() in task.spawn() to execute it asynchronously in a separate thread. This allows the WebSocket handler to return immediately while the game starts running in the background.

Changes

• Modified plugin/src/handlers/run.luau to use task.spawn() for RunService:Run()

[github-actions]

Bridge benchmark — this PR vs base (main)

Same-runner, back-to-back run of the command hot path (dispatch → queue → plugin takes command → response → resolve) with an in-process simulated plugin.

Sequential round-trip latency (smaller is better)

metric	base	this PR	change
p50	0.008 ms	0.013 ms	+62.5% 🔺
p90	0.009 ms	0.014 ms	+55.6% 🔺
p99	0.051 ms	0.041 ms	-19.6% 🔻
mean	0.009 ms	0.014 ms	+55.6% 🔺

Serial throughput (bigger is better)

metric	base	this PR	change
ops/sec	90218 ops/s	85749 ops/s	-5.0% 🔻 worse

⚠️ Possible regression — latency or throughput moved by more than 20%. Please review whether this PR slows down the bridge.

Microbenchmark — small deltas (a few %) are runner noise. Measures the local bridge only; a real Studio plugin adds DataModel + network time. Node base v20.20.2 / head v20.20.2.