feat: slime enemies — jump AI, contact damage, combat system

New entity: Slime (EntityKind::Slime)
- 19 parts: blobby body (3x5) + 2 glowing eyes
- Green translucent colors, brighter center
- HP: 25, spawns every 45 ticks (max 2 alive)

Slime AI (update_slime_ai):
- Jumps toward player every 60 ticks when within 40 cells
- Jump power scales with proximity (closer = stronger)
- Pauses horizontally between jumps (50/50 hop-stop cycle)
- Uses set_horizontal_vel + set_vertical_vel (vector movement)

Combat system (update_combat):
- AABB overlap check between player and all alive enemies
- Goblin: 8 damage per 20 ticks on contact
- Slime: 5 damage per 20 ticks on contact
- Knockback: player pushed away from enemy on hit
- Player.take_damage() called, death possible from enemies

World gen: try_spawn_slime() spawns at surface, 18 cells from player
Renderers: slime rendered as 's' in ascii/terminal, green blob in graphics

6 new tests (122 total, 0 failures)

tests/slime.rs

@@ -0,0 +1,138 @@
+use verbatim::ai::AiAction;
+use verbatim::ai::GameSession;
+
+fn setup() -> GameSession {
+    let mut s = GameSession::new_seeded(42);
+    s.init_empty();
+    s.clear_area(90, 90, 50, 50);
+    s.perform_action(&AiAction::FillRect {
+        x: 80,
+        y: 130,
+        w: 80,
+        h: 15,
+        material: "stone".into(),
+    });
+    s
+}
+
+#[test]
+fn slime_spawns_correctly() {
+    let mut s = setup();
+    s.perform_action(&AiAction::Spawn {
+        kind: "slime".into(),
+        x: 120.0,
+        y: 120.0,
+    });
+    let entities = s.get_entities();
+    let slime = entities.into_iter().find(|e| e.kind == "Slime");
+    assert!(slime.is_some(), "slime should exist after spawn");
+    let sl = slime.unwrap();
+    assert!(sl.alive, "slime should be alive");
+    assert_eq!(sl.max_health, 25.0, "slime max health should be 25");
+}
+
+#[test]
+fn slime_takes_damage_and_dies() {
+    let mut s = setup();
+    s.perform_action(&AiAction::Spawn {
+        kind: "slime".into(),
+        x: 120.0,
+        y: 120.0,
+    });
+    s.step(10);
+    let id = s
+        .get_entities()
+        .into_iter()
+        .find(|e| e.kind == "Slime")
+        .unwrap()
+        .id;
+    s.perform_action(&AiAction::DamageEntity { id, amount: 25.0 });
+    s.step(1);
+    let entities = s.get_entities();
+    let sl = entities.into_iter().find(|e| e.id == id).unwrap();
+    assert!(!sl.alive, "slime should die after 25 damage");
+    assert_eq!(sl.kind, "Corpse", "dead slime should become corpse");
+}
+
+#[test]
+fn slime_jumps_toward_player() {
+    let mut s = setup();
+    s.step(30);
+    let player = s.get_player().unwrap();
+    let px = player.pos[0];
+    s.perform_action(&AiAction::Spawn {
+        kind: "slime".into(),
+        x: px + 10.0,
+        y: 120.0,
+    });
+    s.step(10);
+    let entities = s.get_entities();
+    let slime = entities.into_iter().find(|e| e.kind == "Slime" && e.alive);
+    assert!(slime.is_some(), "slime should be alive");
+    let slime_y_before = slime.unwrap().pos[1];
+    s.step(60);
+    let entities = s.get_entities();
+    let slime_after = entities.into_iter().find(|e| e.kind == "Slime" && e.alive);
+    if let Some(sl) = slime_after {
+        assert!(
+            sl.pos[1] < slime_y_before + 5.0 || sl.pos[0] != px + 10.0,
+            "slime should have moved (jumped) from original position"
+        );
+    }
+}
+
+#[test]
+fn slime_deals_contact_damage_to_player() {
+    let mut s = setup();
+    s.step(30);
+    let player = s.get_player().unwrap();
+    let hp_before = player.health;
+    s.perform_action(&AiAction::Spawn {
+        kind: "slime".into(),
+        x: player.pos[0] + 1.0,
+        y: player.pos[1],
+    });
+    s.step(60);
+    let player_after = s.get_player().unwrap();
+    assert!(
+        player_after.health < hp_before,
+        "player should take damage from slime contact: {} -> {}",
+        hp_before,
+        player_after.health
+    );
+}
+
+#[test]
+fn slime_template_has_correct_shape() {
+    use verbatim::entity::body_template::BodyTemplate;
+    let t = BodyTemplate::slime();
+    assert_eq!(t.name, "slime");
+    assert!(
+        t.parts.len() >= 15,
+        "slime should have 15+ parts, got {}",
+        t.parts.len()
+    );
+    assert!(
+        t.parts.iter().any(|p| p.label == "eye"),
+        "slime should have eyes"
+    );
+}
+
+#[test]
+fn slime_count_in_world() {
+    let mut s = setup();
+    for i in 0..3 {
+        s.perform_action(&AiAction::Spawn {
+            kind: "slime".into(),
+            x: 100.0 + i as f32 * 10.0,
+            y: 120.0,
+        });
+    }
+    s.step(10);
+    let slimes = s
+        .get_entities()
+        .into_iter()
+        .filter(|e| e.kind == "Slime")
+        .count();
+    assert_eq!(slimes, 3, "should have 3 slimes");
+}