Block scripts and triggers: data model, Rhai translation and runtime

Editor missions keep a painted map or roll a random map per campaign run,
leave out goals they cannot have, and run their triggers in the fixed step.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

lang/en.lang

@@ -883,6 +883,8 @@ msg.tool_research = Not researched yet - creatures studying in the library work
 msg.script = {0}
 msg.script_objective = Objective: {0}
 msg.script_error = Script error: {0}
+msg.script_hint = Crookfinger: {0}
+msg.mission_start_custom = Mission: {0}
 msg.script_language = Unsupported mission script language: {0}
 
 # spells