fix(mcp): add diff_versions to TOOL_ANNOTATIONS as read-only idempotent

Signed-off-by: Thomas Dyar <tdyar@intersystems.com>

Author: isc-tdyar

src/mcp/mcp.c

@@ -629,6 +629,7 @@ static const tool_annotation_def_t TOOL_ANNOTATIONS[] = {
     {"detect_changes", false, true, true, false},
     {"manage_adr", false, true, false, false},
     {"ingest_traces", false, false, false, false},
+    {"diff_versions", true, false, true, false},
 };
 
 static const tool_annotation_def_t *mcp_tool_annotations(const char *name) {

tests/test_mcp.c

@@ -338,7 +338,7 @@ TEST(mcp_tools_have_behavior_annotations) {
         {"detect_changes", false, true, true, false},
         {"manage_adr", false, true, false, false},
         {"ingest_traces", false, false, false, false},
-        {"diff_versions", false, true, true, false},
+        {"diff_versions", true, false, true, false},
     };
 
     char *json = cbm_mcp_tools_list();