fix: CVM subscription #p array format + WS response + use-after-free

Critical fixes for CVM MCP roundtrip over Nostr relay:
- Fix subscription filter: #p must be array not string (relay rejected with 'bad req')
- Publish MCP responses via existing WS connection instead of opening new TLS
- Fix use-after-free: tags_str freed before nostr_event_to_json used it
- Pass esp_tls_t through process_relay_message -> handle_mcp_message chain

Verified on Board B via relay.primal.net:
- MCP initialize roundtrip: PASS
- tools/call get_config: PASS (returns device config)
- tools/call get_balance: PASS (returns balance_sats, proof_count)
- CEP-6 announcements (kinds 11316, 11317, 10002): all accepted by relay

1 files changed, 69 insertions, 9 deletions

diff --git a/main/cvm_server.c b/main/cvm_server.c
index dd04047..96ce7d3 100644
--- a/main/cvm_server.c
+++ b/main/cvm_server.c
@@ -323,6 +323,54 @@ static esp_err_t publish_event_to_relay(const char *relay_url, const char *event
     return ESP_OK;
 }
 
+static esp_err_t publish_kind_25910_response_ws(esp_tls_t *tls,
+                                                  const char *content_json,
+                                                  const char *request_event_id)
+{
+    const tollgate_identity_t *id = identity_get();
+    if (!id || !id->initialized) return ESP_FAIL;
+
+    cJSON *tags = cJSON_CreateArray();
+    cJSON *e_tag = cJSON_CreateArray();
+    cJSON_AddItemToArray(e_tag, cJSON_CreateString("e"));
+    cJSON_AddItemToArray(e_tag, cJSON_CreateString(request_event_id));
+    cJSON_AddItemToArray(tags, e_tag);
+
+    char *tags_str = cJSON_PrintUnformatted(tags);
+    cJSON_Delete(tags);
+
+    nostr_event_t event;
+    nostr_event_init(&event, id->npub_hex, 25910, tags_str, content_json);
+    nostr_event_sign(&event, id->nsec);
+
+    char *event_json = malloc(8192);
+    if (!event_json) {
+        free(tags_str);
+        return ESP_ERR_NO_MEM;
+    }
+
+    esp_err_t ret = nostr_event_to_json(&event, event_json, 8192);
+    free(tags_str);
+    if (ret != ESP_OK) {
+        free(event_json);
+        return ret;
+    }
+
+    size_t msg_len = 10 + strlen(event_json) + 2;
+    char *msg = malloc(msg_len);
+    if (!msg) {
+        free(event_json);
+        return ESP_ERR_NO_MEM;
+    }
+    snprintf(msg, msg_len, "[\"EVENT\",%s]", event_json);
+    ESP_LOGI(TAG, "Sending WS response (%d bytes)", (int)strlen(msg));
+    int rc = ws_send_text(tls, msg);
+    ESP_LOGI(TAG, "WS send result: %d", rc);
+    free(msg);
+    free(event_json);
+    return ESP_OK;
+}
+
 static esp_err_t publish_kind_25910_response(const char *relay_url,
                                               const char *content_json,
                                               const char *request_event_id)
@@ -366,7 +414,7 @@ static bool is_owner_pubkey(const char *pubkey_hex)
     return strcmp(id->npub_hex, pubkey_hex) == 0;
 }
 
-static void handle_mcp_message(const char *relay_url, const char *sender_pubkey,
+static void handle_mcp_message(esp_tls_t *tls, const char *sender_pubkey,
                                 const char *event_id, const char *content)
 {
     cJSON *msg = cJSON_Parse(content);
@@ -386,14 +434,20 @@ static void handle_mcp_message(const char *relay_url, const char *sender_pubkey,
         if (strcmp(m, "initialize") == 0) {
             ESP_LOGI(TAG, "MCP initialize from %s", sender_pubkey);
             char *resp = build_initialize_response(id_str, sender_pubkey);
-            publish_kind_25910_response(relay_url, resp, event_id);
+            if (tls) {
+                publish_kind_25910_response_ws(tls, resp, event_id);
+            } else {
+                ESP_LOGW(TAG, "No TLS for response");
+            }
             free(resp);
         } else if (strcmp(m, "notifications/initialized") == 0) {
             ESP_LOGI(TAG, "Client initialized: %s", sender_pubkey);
         } else if (strcmp(m, "tools/list") == 0) {
             ESP_LOGI(TAG, "tools/list from %s", sender_pubkey);
             char *resp = build_tools_list_response(id_str);
-            publish_kind_25910_response(relay_url, resp, event_id);
+            if (tls) {
+                publish_kind_25910_response_ws(tls, resp, event_id);
+            }
             free(resp);
         } else if (strcmp(m, "tools/call") == 0) {
             cJSON *params = cJSON_GetObjectItem(msg, "params");
@@ -414,12 +468,16 @@ static void handle_mcp_message(const char *relay_url, const char *sender_pubkey,
 
                 mcp_response_t mcp_resp = mcp_dispatch(&req);
                 char *resp = build_tool_call_response(id_str, &mcp_resp);
-                publish_kind_25910_response(relay_url, resp, event_id);
+                if (tls) {
+                    publish_kind_25910_response_ws(tls, resp, event_id);
+                }
                 free(resp);
             }
         } else if (strcmp(m, "ping") == 0) {
             char *resp = build_ping_response(id_str);
-            publish_kind_25910_response(relay_url, resp, event_id);
+            if (tls) {
+                publish_kind_25910_response_ws(tls, resp, event_id);
+            }
             free(resp);
         } else {
             ESP_LOGW(TAG, "Unknown MCP method: %s", m);
@@ -433,7 +491,7 @@ static void handle_mcp_message(const char *relay_url, const char *sender_pubkey,
     cJSON_Delete(msg);
 }
 
-static void process_relay_message(const char *relay_url, const char *msg_str)
+static void process_relay_message(esp_tls_t *tls, const char *relay_url, const char *msg_str)
 {
     cJSON *arr = cJSON_Parse(msg_str);
     if (!arr || !cJSON_IsArray(arr)) {
@@ -492,7 +550,7 @@ static void process_relay_message(const char *relay_url, const char *msg_str)
         return;
     }
 
-    handle_mcp_message(relay_url, pubkey->valuestring, event_id->valuestring, content->valuestring);
+    handle_mcp_message(tls, pubkey->valuestring, event_id->valuestring, content->valuestring);
     cJSON_Delete(arr);
 }
 
@@ -505,7 +563,9 @@ static esp_err_t subscribe_to_relay(esp_tls_t *tls, const char *npub)
     cJSON *kinds = cJSON_CreateArray();
     cJSON_AddItemToArray(kinds, cJSON_CreateNumber(25910));
     cJSON_AddItemToObject(filter, "kinds", kinds);
-    cJSON_AddStringToObject(filter, "#p", npub);
+    cJSON *p_tags = cJSON_CreateArray();
+    cJSON_AddItemToArray(p_tags, cJSON_CreateString(npub));
+    cJSON_AddItemToObject(filter, "#p", p_tags);
     cJSON_AddNumberToObject(filter, "limit", 100);
     cJSON_AddItemToArray(sub, filter);
 
@@ -567,7 +627,7 @@ static void cvm_relay_task(void *arg)
                 char *text = parse_ws_text_frame(buf, rlen);
                 if (text) {
                     if (strlen(text) > 0) {
-                        process_relay_message(relay_url, text);
+                        process_relay_message(tls, relay_url, text);
                     }
                     free(text);
                 }