fix(studio-bridge): avoid Handlebars parse error in plugin template

Handlebars interprets Luau's ~= operator followed by "{{" as its
whitespace-stripping ~{{ syntax. Build the template sentinel string
from parts so ~= is never adjacent to {{.

Author: Quenty

tools/studio-bridge/templates/studio-bridge-plugin/src/StudioBridgePlugin.server.lua

@@ -26,7 +26,8 @@ local ExecuteAction = require(script.Parent.Actions.ExecuteAction)
 -- Build constants (Handlebars templates before substitution)
 local PORT = "{{PORT}}"
 local SESSION_ID = "{{SESSION_ID}}"
-local IS_EPHEMERAL = (PORT ~= "{{" .. "PORT" .. "}}")
+local _PORT_TEMPLATE = "{" .. "{PORT}" .. "}"
+local IS_EPHEMERAL = (PORT ~= _PORT_TEMPLATE)
 
 -- Only run inside Studio
 if not RunService:IsStudio() then