MCP: mark detect read-only (was defaulting to destructive)

Unannotated MCP tools default to readOnlyHint:false/destructiveHint:true, so
clients would gate detect behind confirmation. detect only fetches a domain's
public surface — annotate it readonly + non-destructive + idempotent so
clients can auto-run it.

Author: RhysSullivan

worker/registry.ts

@@ -14,7 +14,12 @@ const Detect = Tool.make("detect", {
   description: DETECT_DESCRIPTION,
   parameters: DetectParams,
   success: DetectionResult,
-});
+})
+  // detect only fetches a domain's public surface — safe to auto-run.
+  .annotate(Tool.Readonly, true)
+  .annotate(Tool.Destructive, false)
+  .annotate(Tool.Idempotent, true);
+// openWorldHint stays true (default): it reaches arbitrary external domains.
 
 export const toolkit = Toolkit.make(Detect);