refactor(tests): improve functional test documentation and cleanup

- Add detailed documentation about test isolation in functionaltests.c
- Improve comments in proftest.c: buffer size explanation, stabber sync TODO
- Add reference to stabber issue #1 for stbbr_wait_stopped() API
- Document prof_output_regex() usage rationale in test_muc.c
- Enhance ping_server test comments for clarity
- Update CONTRIBUTING.md: fix function names (prof_output_regex, prof_timeout)
- Remove redundant commented-out test configurations from ci-build.sh
- Remove obsolete stabber recv suppressions from prof.supp (issue fixed)
- Add clear explanation for disabled assertion in test_chat_session.c
- Add comment explaining /connect max args in cmd_defs.c

tests/functionaltests/test_ping.c

@@ -11,8 +11,13 @@
 void
 ping_server(void **state)
 {
-    // This test verifies that profanity correctly handles the /ping command
-    // when the server supports ping (urn:xmpp:ping feature)
+    /*
+     * This test verifies that profanity correctly handles the /ping command
+     * when the server supports ping (urn:xmpp:ping feature).
+     * 
+     * We register disco#info response with ping support, then verify
+     * profanity sends ping and receives "Pinged server" confirmation.
+     */
     
     // Register disco#info response that includes ping support
     stbbr_for_query("http://jabber.org/protocol/disco#info",
@@ -31,15 +36,18 @@ ping_server(void **state)
 
     prof_connect();
     
-    // Wait for disco#info exchange to complete
+    /*
+     * Wait for disco#info exchange to complete.
+     * TODO: Replace with proper wait mechanism (e.g., wait for capabilities
+     * to be cached). Currently we use sleep to ensure disco#info response
+     * is processed before sending /ping command.
+     */
     sleep(3);
 
-    // Send ping command - should either work or report server doesn't support it
     prof_input("/ping");
     
     prof_timeout(10);
-    // Accept either outcome: ping was sent OR server doesn't support
-    assert_true(prof_output_regex("Ping|Server does not support"));
+    assert_true(prof_output_regex("Pinged server"));
     prof_timeout_reset();
 }