feat(server): add loaded locations debug endpoint

packages/protocol/src/groups/debug.ts

@@ -0,0 +1,15 @@
+import { Location } from "@opencode-ai/schema/location"
+import { Schema } from "effect"
+import { HttpApiEndpoint, HttpApiGroup, OpenApi } from "effect/unstable/httpapi"
+
+export const DebugGroup = HttpApiGroup.make("server.debug").add(
+  HttpApiEndpoint.get("debug.location", "/api/debug/location", {
+    success: Schema.Array(Location.Ref),
+  }).annotateMerge(
+    OpenApi.annotations({
+      identifier: "v2.debug.location",
+      summary: "List loaded locations",
+      description: "List locations currently loaded by the server.",
+    }),
+  ),
+)