refactor(tests): migrate to content-based stubbing

- Replace stbbr_for_id() with stbbr_for_query()/stbbr_send()
- Content-based stubbing matches stanzas by namespace instead of ID
- Use regex assertions for flexible output matching
- Fix timing issues in chat_session and presence tests

tests/functionaltests/test_receipts.c

@@ -4,7 +4,6 @@
 #include <string.h>
 
 #include <stabber.h>
-#include <expect.h>
 
 #include "proftest.h"
 
@@ -31,8 +30,9 @@ send_receipt_request(void **state)
 
     prof_connect();
 
-    stbbr_for_id("prof_caps_4",
-        "<iq from='buddy1@localhost/laptop' to='stabber@localhost' id='prof_caps_4' type='result'>"
+    // Register disco#info response for capabilities query (receipts support)
+    stbbr_for_query("http://jabber.org/protocol/disco#info",
+        "<iq from='buddy1@localhost/laptop' to='stabber@localhost' id='*' type='result'>"
             "<query xmlns='http://jabber.org/protocol/disco#info' node='http://profanity-im.github.io#hAkb1xZdJV9BQpgGNw8zG5Xsals='>"
                 "<identity category='client' name='Profanity 0.5.0' type='console'/>"
                 "<feature var='urn:xmpp:receipts'/>"