feat: log tree from Module 2 (logTree / log_tree); SpellGrid CLIs print Log:

Engine events carry the nesting depth they were recorded at; the harness
prints the log as an indented tree. New tests test_02_log_tree_shows_nesting
and test_03_log_tree_death_phase; both SpellGrid CLIs print the tree of the
last command's Sequences under a Log: line.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

course/10-spellgrid/reference/rust/tests/cli.rs

@@ -53,6 +53,30 @@ fn cli_wins_level_2_with_choices_and_play() {
     assert!(out.contains("Hand: Ember Moth (Assembled)"));
 }
 
+#[test]
+fn cli_prints_the_log_tree_of_each_command() {
+    let level = include_str!("../levels/l1-double-tap.json");
+    let (_, out) = play(level, &["w", "w", "c Whirlwind", "q"]);
+    // The moves run no Sequence, so only the cast prints a log: its tree, Deathrattles nested.
+    assert_eq!(out.matches("Log:\n").count(), 1, "{out}");
+    let tree = [
+        "Log:",
+        "SpellCast{card: \"Whirlwind\"}",
+        "Damaged{target: 32, amount: 1}",
+        "Damaged{target: 33, amount: 1}",
+        "Destroyed{id: 32}",
+        "DeathPhase{round: 1}",
+        "Triggered{source: 32, trigger: \"deathrattle\"}",
+        "  Damaged{target: 33, amount: 1}",
+        "Triggered{source: 32, trigger: \"deathrattle\"}",
+        "  Damaged{target: 33, amount: 1}",
+        "Destroyed{id: 33}",
+        "DeathPhase{round: 2}",
+        "",
+    ];
+    assert!(out.contains(&tree.join("\n")), "{out}");
+}
+
 #[test]
 fn cli_reports_errors_and_quits() {
     let input = ["c Spark", "x", "q"];