llama-atmosphere-agent: assert the plain-chat integration test on behaviour, not wording

TODO.md

@@ -19,12 +19,9 @@ so everything below is genuinely still open.
 
 ### Atmosphere coding agent (`llama-atmosphere-agent/`) — follow-ups
 
-The headless loop is verified (see CLAUDE.md "Local coding agent with Atmosphere"). Still open:
+The headless loop is verified, including the model-backed CI job (run 35600558852: tool call
+answered, read→write→read loop changed the file). Still open:
 
-- **First model-backed CI run.** `test-java-llama-atmosphere-agent-integration` was added without a
-  run on GitHub's runners; the three assertions are about the loop (tool invoked, result answered,
-  file changed), but a 1.5B model on a CPU runner may still need a prompt or budget tweak. Read its
-  first run before trusting it as a signal.
 - **Tool rounds are not carried across REPL turns** — only `user`/`assistant` text is replayed, so a
   second question cannot refer to a tool result of the first. Keep the full Atmosphere
   `ChatMessage` list (incl. `tool_calls`/`tool` messages) per turn instead.

llama-atmosphere-agent/src/test/java/net/ladenthin/llama/atmosphere/AtmosphereToolLoopIntegrationTest.java

@@ -116,16 +116,23 @@ private ConsoleSession session() {
         return new ConsoleSession(new PrintStream(new ByteArrayOutputStream(), true, StandardCharsets.UTF_8), fs);
     }
 
+    /**
+     * Plain chat: a non-empty answer that arrives as several streamed chunks. The first CI run (run
+     * 35600558852) showed why this must not pin wording: asked to "reply with exactly ATMOSPHERE_OK", the
+     * 1.5B model streamed {@code OK} — a perfectly working loop failing a prose assertion. What the wire
+     * contract guarantees is that the question reaches the model and its answer streams back, so that
+     * is what is asserted; the one content check is a fact no instruct model gets wrong.
+     */
     @Test
     void plainChatStreamsAnAnswer() throws Exception {
         ConsoleSession session = session();
 
-        runner(List.of()).run("Reply with exactly this word and nothing else: ATMOSPHERE_OK", List.of(), session);
+        runner(List.of()).run("What is 2 + 2? Answer with one short sentence.", List.of(), session);
 
         assertThat(session.await(TURN_TIMEOUT), is(true));
         assertThat(session.failure(), is(nullValue()));
-        assertThat(
-                "streamed text: " + session.text(), session.text().toUpperCase().contains("ATMOSPHERE_OK"), is(true));
+        assertThat("streamed text: " + session.text(), session.text().trim().isEmpty(), is(false));
+        assertThat("the answer must contain the number 4: " + session.text(), session.text(), containsString("4"));
         assertThat(
                 "the answer must arrive as several SSE chunks, not one blob",
                 session.chunks().size(),