fix(ai): bound response parsing and harden AUTO fallback errors

- bound _parse_responses scans to the output_text part's object and to
  the content array, so a later sibling item's "text" (e.g. a reasoning
  summary) can never be returned as the assistant reply
- do not retry the other flavour on a curl timeout: the request likely
  reached the server and may still be generating, so a re-POST of the
  conversation could trigger a second billed generation
- remember an unparseable 2xx from the first AUTO attempt and surface
  stashed first-attempt errors in both error paths, instead of showing
  only the final attempt's transport or HTTP error
- recognize Ollama's model-not-found wording in _names_model so a model
  typo is not misread as a missing endpoint
- drop the dead, racy provider-lookup fallback in the generic request
  thread: a missing provider ref is a caller bug and now fails loudly
- fix ai_providers_lists_defaults to expect the header the command
  actually prints ("Configured providers:"); the test was broken since
  its introduction but CI never ran it
- add functional test group 5 (AI command surface) to FUNC_TEST_GROUPS
  so the CI parallel target runs it; proftest.c port ranges already
  account for five groups

tests/functionaltests/test_ai.c

@@ -55,11 +55,11 @@ ai_no_args_shows_help(void** state)
 void
 ai_providers_lists_defaults(void** state)
 {
-    /* `/ai providers` (no "list") shows the built-in list with URLs. */
+    /* `/ai providers` (no "list") shows the configured list with URLs. */
     prof_input("/ai providers");
 
     prof_timeout(5);
-    assert_true(prof_output_exact("Available AI providers:"));
+    assert_true(prof_output_exact("Configured providers:"));
     /* At least one URL line is rendered — exact name agnostic. */
     assert_true(prof_output_regex("https?://"));
     prof_timeout_reset();

tests/unittests/test_ai_client.c

@@ -1087,6 +1087,48 @@ test_ai_parse_response_responses_reasoning_only_returns_null(void** state)
     assert_null(out);
 }
 
+void
+test_ai_parse_response_responses_reasoning_after_message_skipped(void** state)
+{
+    /* A reasoning item ordered after the message, with the part's "text"
+     * preceding "type":"output_text": the forward scan must stay inside the
+     * part's object and the backscan must find the real answer. */
+    const gchar* json = "{\"output\":["
+                        "{\"type\":\"message\",\"content\":[{\"text\":\"answer\",\"type\":\"output_text\"}]},"
+                        "{\"type\":\"reasoning\",\"summary\":[{\"type\":\"summary_text\",\"text\":\"secret\"}]}"
+                        "]}";
+    auto_gchar gchar* out = ai_parse_response(json);
+    assert_non_null(out);
+    assert_string_equal("answer", out);
+}
+
+void
+test_ai_parse_response_responses_empty_content_not_leaked(void** state)
+{
+    /* An empty content array followed by a reasoning item must yield a parse
+     * failure; the scan must not escape the array and return the summary. */
+    const gchar* json = "{\"output\":["
+                        "{\"type\":\"message\",\"content\":[]},"
+                        "{\"type\":\"reasoning\",\"summary\":[{\"type\":\"summary_text\",\"text\":\"secret\"}]}"
+                        "]}";
+    gchar* out = ai_parse_response(json);
+    assert_null(out);
+}
+
+void
+test_ai_parse_response_responses_text_value_before_later_item(void** state)
+{
+    /* A reply that is exactly "text" plus a reasoning item after the message:
+     * the backscan's own extraction must also stay inside the part's object. */
+    const gchar* json = "{\"output\":["
+                        "{\"type\":\"message\",\"content\":[{\"text\":\"text\",\"type\":\"output_text\"}]},"
+                        "{\"type\":\"reasoning\",\"summary\":[{\"type\":\"summary_text\",\"text\":\"secret\"}]}"
+                        "]}";
+    auto_gchar gchar* out = ai_parse_response(json);
+    assert_non_null(out);
+    assert_string_equal("text", out);
+}
+
 void
 test_ai_parse_response_choices_in_string_value(void** state)
 {

tests/unittests/test_ai_client.h

@@ -79,6 +79,9 @@ void test_ai_parse_response_responses_brace_in_text(void** state);
 void test_ai_parse_response_choices_logprobs_before_content(void** state);
 void test_ai_parse_response_reasoning_not_leaked_without_text(void** state);
 void test_ai_parse_response_responses_reasoning_only_returns_null(void** state);
+void test_ai_parse_response_responses_reasoning_after_message_skipped(void** state);
+void test_ai_parse_response_responses_empty_content_not_leaked(void** state);
+void test_ai_parse_response_responses_text_value_before_later_item(void** state);
 void test_ai_parse_response_responses_text_value_text(void** state);
 void test_ai_parse_response_escaped_quote(void** state);
 void test_ai_parse_response_newline_escape(void** state);

tests/unittests/unittests.c

@@ -789,6 +789,9 @@ main(int argc, char* argv[])
         cmocka_unit_test(test_ai_parse_response_choices_logprobs_before_content),
         cmocka_unit_test(test_ai_parse_response_reasoning_not_leaked_without_text),
         cmocka_unit_test(test_ai_parse_response_responses_reasoning_only_returns_null),
+        cmocka_unit_test(test_ai_parse_response_responses_reasoning_after_message_skipped),
+        cmocka_unit_test(test_ai_parse_response_responses_empty_content_not_leaked),
+        cmocka_unit_test(test_ai_parse_response_responses_text_value_before_later_item),
         cmocka_unit_test(test_ai_parse_response_responses_text_value_text),
         cmocka_unit_test(test_ai_parse_response_escaped_quote),
         cmocka_unit_test(test_ai_parse_response_newline_escape),