CB-WP-0018-T02: a game log the player can read

bot::Journal -- a shared list of Applied { actor, command, events } the
driver appends to via play_journaled; play delegates with None so
nothing existing changed. BotGame.events only appears after play
returns, which is no use to a page rendered mid-game.

Phrased with record::to_step, the recorder's vocabulary, so what the
player reads is what the scenario file will say, and all 29 GroundEvent
variants now render in words instead of Debug.

A command that produced no events says 'no effect'; the mutation
dropping that branch goes red. Honest limitation recorded: the reported
SOLVE case is resolved inside the system's resolve command, which does
produce events for other seats, so it shows as a selection with no claim
following rather than an explicit 'no effect'. Making it explicit would
mean the renderer deciding why a rule did nothing -- a second
implementation of the rules, which this task's control forbids.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

crates/cb-render-html/src/lib.rs

@@ -573,5 +573,59 @@ mod affordances {
     }
 }
 
+#[cfg(test)]
+mod gamelog {
+    //! CB-WP-0018 T02.
+
+    use crate::doc::{document_with_log, LogLine};
+    use cb_kernel::PlayerId;
+
+    fn line(effects: &[&str]) -> LogLine {
+        LogLine {
+            who: "P1".into(),
+            what: "select_action action=SOLVE problem=1".into(),
+            effects: effects.iter().map(|s| (*s).to_string()).collect(),
+        }
+    }
+
+    fn page(log: &[LogLine]) -> String {
+        document_with_log(
+            &crate::testfix::view(Some(PlayerId(0))),
+            &[],
+            "/command?t=x",
+            Some(PlayerId(0)),
+            false,
+            log,
+        )
+    }
+
+    /// **The case the pass was reported for.** A SOLVE that cannot be
+    /// fulfilled produces no events, and a log built only from events
+    /// would render nothing for it — reproducing the silence the
+    /// maintainer hit when the same move did nothing three rounds
+    /// running.
+    #[test]
+    fn a_command_that_produced_nothing_says_so() {
+        let html = page(&[line(&[])]);
+        assert!(
+            html.contains("no effect"),
+            "a command with no events rendered as if it had done something"
+        );
+        let text = crate::text_of(&html);
+        assert!(text.contains("select_action action=SOLVE problem=1"));
+    }
+
+    #[test]
+    fn effects_are_listed_and_an_empty_log_says_it_is_empty() {
+        let text = crate::text_of(&page(&[line(&["problem 1 claimed by P1"])]));
+        assert!(text.contains("problem 1 claimed by P1"));
+        assert!(
+            !text.contains("no effect"),
+            "a command WITH effects was marked as having none"
+        );
+        assert!(crate::text_of(&page(&[])).contains("nothing has happened yet"));
+    }
+}
+
 #[cfg(test)]
 mod testfix;