Fix cross-project target grounding and add handoff note

editor/tests/step615_test.cpp

@@ -1,4 +1,4 @@
-// Step 615: whetstone_generate_taskitems MCP Tool (12 tests)
+// Step 615: whetstone_generate_taskitems MCP Tool (13 tests)
 
 #include "MCPServer.h"
 
@@ -199,6 +199,37 @@ void test_rejects_invalid_requirement_kind() {
     PASS();
 }
 
+void test_cross_project_repo_signal_grounds_target_files() {
+    TEST(cross_project_repo_signal_grounds_target_files);
+    MCPServer mcp;
+    json reqs = json::array({{
+        {"requirementId", "goal-constcad"},
+        {"kind", "goal"},
+        {"normalizedText", "ConstCAD ecosystem integration across cad_orchestrator, hivemind, gleaner, and constcad"},
+        {"anchor", "goals"},
+        {"sourceLine", 1},
+        {"ambiguous", false}
+    }});
+    json out = callTool(mcp, "whetstone_generate_taskitems",
+                        {{"normalizedRequirements", reqs}, {"strictExecutionContract", true}});
+    CHECK(out.value("success", false), "success should be true");
+    const auto& files = out["tasks"][0]["executionContract"]["targetFiles"];
+    bool hasExternal = false;
+    for (const auto& f : files) {
+        if (!f.is_string()) continue;
+        std::string v = f.get<std::string>();
+        if (v.rfind("cad_orchestrator/", 0) == 0 ||
+            v.rfind("hivemind/", 0) == 0 ||
+            v.rfind("gleaner/", 0) == 0 ||
+            v.rfind("constcad/", 0) == 0) {
+            hasExternal = true;
+        }
+        CHECK(v.rfind("editor/src/mcp/", 0) != 0, "should not fallback to editor/src/mcp internal defaults");
+    }
+    CHECK(hasExternal, "expected at least one cross-project target file");
+    PASS();
+}
+
 int main() {
     std::cout << "Step 615: whetstone_generate_taskitems MCP Tool\n";
 
@@ -214,6 +245,7 @@ int main() {
     test_normalized_requirements_must_be_array();            // 10
     test_rejects_empty_normalized_requirements();            // 11
     test_rejects_invalid_requirement_kind();                 // 12
+    test_cross_project_repo_signal_grounds_target_files();   // 13
 
     std::cout << "\nResults: " << passed << "/" << (passed + failed) << " passed\n";
     return failed == 0 ? 0 : 1;