fix(hopper): answer caller-scan methods in the package fixture

The packaged Hopper stand-in echoed unknown bridge methods, so
analyze_function rejected rea_caller_scan_target as an invalid scan
target and the native package baseline returned unreadable_output.

tests/fixtures/fakeHopper.mjs

@@ -112,6 +112,46 @@ const enhancedFixtureResult = (method) => {
       return [{ address: "0x1000", value: "fixture" }];
     case "procedure_pseudo_code":
       return "return 0;";
+    case "rea_caller_scan_target":
+      return {
+        target: {
+          address: "0x1000",
+          name: "fixture",
+          symbol: null,
+          classification: null,
+          body: {
+            available: false,
+            reason: "The fixture has no function body-extent observation.",
+          },
+        },
+        instructions: ["0x1000"],
+        instructions_complete: true,
+      };
+    case "rea_caller_base":
+      return {
+        target: {
+          address: "0x1000",
+          name: "fixture",
+          symbol: null,
+          classification: null,
+          body: {
+            available: false,
+            reason: "The fixture has no function body-extent observation.",
+          },
+        },
+        instructions: ["0x1000"],
+        instructions_complete: true,
+        callers: [],
+        callers_complete: true,
+      };
+    case "rea_caller_scan_page":
+      return {
+        start: 0,
+        next: 0,
+        total: 0,
+        oversized: false,
+        items: [],
+      };
     case "analyze_function": {
       return {
         procedure: {