fix(mcp): crash on 0-edge nodes + fuzzy name fallback in trace

Fix crash (double-free) when tracing nodes with 0 in-degree and 0 out-degree
(e.g. Type nodes, empty Class stubs). Detect early via cbm_store_node_degree
and return basic match info without attempting BFS traversal. Also move the
traversal result array from stack to heap to prevent stack smashing with
many start IDs.

Add fuzzy name fallback: when exact name match returns 0 results, run a
regex search with '.*name.*' pattern and return up to 10 suggestions with
name, label, file_path, line. This handles cases like searching for
'RecordingSession' when only 'ContinuousRecordingSessionDataGen' exists.

Author: Your Name

src/mcp/mcp.c

@@ -1660,9 +1660,53 @@ static char *handle_trace_call_path(cbm_mcp_server_t *srv, const char *args) {
     cbm_store_find_nodes_by_name(store, project, func_name, &nodes, &node_count);
 
     if (node_count == 0) {
-        free(func_name);
-        free(project);
-        free(direction);
+        /* Fuzzy fallback: try substring match when exact name not found.
+         * This handles cases like searching for "RecordingSession" when only
+         * "ContinuousRecordingSessionDataGen" exists. */
+        cbm_search_params_t fuzzy = {0};
+        char pattern[512];
+        snprintf(pattern, sizeof(pattern), ".*%s.*", func_name);
+        fuzzy.project = project;
+        fuzzy.name_pattern = pattern;
+        fuzzy.limit = 10;
+        cbm_search_output_t fuzzy_results = {0};
+        cbm_store_search(store, &fuzzy, &fuzzy_results);
+
+        if (fuzzy_results.count > 0) {
+            /* Return fuzzy matches as suggestions */
+            yyjson_mut_doc *fdoc = yyjson_mut_doc_new(NULL);
+            yyjson_mut_val *froot = yyjson_mut_obj(fdoc);
+            yyjson_mut_doc_set_root(fdoc, froot);
+            yyjson_mut_obj_add_str(fdoc, froot, "status", "not_found_exact");
+            char msg[512];
+            snprintf(msg, sizeof(msg),
+                     "No exact match for '%s'. Found %d partial matches — "
+                     "use one of these exact names:", func_name, fuzzy_results.count);
+            yyjson_mut_obj_add_strcpy(fdoc, froot, "message", msg);
+            yyjson_mut_val *suggestions = yyjson_mut_arr(fdoc);
+            for (int i = 0; i < fuzzy_results.count; i++) {
+                yyjson_mut_val *si = yyjson_mut_obj(fdoc);
+                yyjson_mut_obj_add_strcpy(fdoc, si, "name",
+                    fuzzy_results.results[i].node.name ? fuzzy_results.results[i].node.name : "");
+                yyjson_mut_obj_add_strcpy(fdoc, si, "label",
+                    fuzzy_results.results[i].node.label ? fuzzy_results.results[i].node.label : "");
+                yyjson_mut_obj_add_strcpy(fdoc, si, "file_path",
+                    fuzzy_results.results[i].node.file_path ? fuzzy_results.results[i].node.file_path : "");
+                yyjson_mut_obj_add_int(fdoc, si, "line", fuzzy_results.results[i].node.start_line);
+                yyjson_mut_arr_add_val(suggestions, si);
+            }
+            yyjson_mut_obj_add_val(fdoc, froot, "suggestions", suggestions);
+            char *fjson = yy_doc_to_str(fdoc);
+            yyjson_mut_doc_free(fdoc);
+            cbm_store_search_free(&fuzzy_results);
+            free(func_name); free(project); free(direction);
+            cbm_store_free_nodes(nodes, 0);
+            char *result = cbm_mcp_text_result(fjson, false);
+            free(fjson);
+            return result;
+        }
+        cbm_store_search_free(&fuzzy_results);
+        free(func_name); free(project); free(direction);
         cbm_store_free_nodes(nodes, 0);
         return cbm_mcp_text_result("{\"error\":\"function not found\"}", true);
     }
@@ -1792,6 +1836,25 @@ static char *handle_trace_call_path(cbm_mcp_server_t *srv, const char *args) {
         yyjson_mut_obj_add_val(doc, root, "candidates", cands);
     }
 
+    /* Check if the node has any edges at all. If not, return basic info only.
+     * This avoids BFS crashes on nodes with 0 edges (e.g. Type nodes, empty Classes). */
+    {
+        int in_deg = 0;
+        int out_deg = 0;
+        cbm_store_node_degree(store, nodes[best_idx].id, &in_deg, &out_deg);
+        if (in_deg == 0 && out_deg == 0) {
+            /* No edges — return basic info */
+            char *json = yy_doc_to_str(doc);
+            yyjson_mut_doc_free(doc);
+            free(start_ids);
+            cbm_store_free_nodes(nodes, node_count);
+            free(func_name); free(project); free(direction);
+            char *result = cbm_mcp_text_result(json, false);
+            free(json);
+            return result;
+        }
+    }
+
     /* ── Categorized edge query: like GitNexus context() ──
      * Instead of flat BFS, query each edge type separately and return
      * categorized results: incoming.calls, incoming.imports, incoming.extends,
@@ -1810,8 +1873,7 @@ static char *handle_trace_call_path(cbm_mcp_server_t *srv, const char *args) {
 
     /* Collect all traversal results for lifetime management */
     #define MAX_TR 64
-    cbm_traverse_result_t all_tr[MAX_TR];
-    memset(all_tr, 0, sizeof(all_tr));
+    cbm_traverse_result_t *all_tr = calloc(MAX_TR, sizeof(cbm_traverse_result_t));
     int tr_count = 0;
 
     if (do_inbound) {
@@ -2047,6 +2109,7 @@ static char *handle_trace_call_path(cbm_mcp_server_t *srv, const char *args) {
     for (int t = 0; t < tr_count; t++) {
         cbm_store_traverse_free(&all_tr[t]);
     }
+    free(all_tr);
     #undef EDGE_QUERY_MAX
     #undef MAX_TR