Add scripted lightning weapon mods with interpolated anchored effects

mods/lightning_cannon/scripts/equipment.rhai

@@ -0,0 +1,6 @@
+// Pickups use the same reusable equipment as the shop.
+fn on_pickup(event, state, random) {
+    let recovered = if state.contains("recovered") { state.recovered % 100000 + 1 } else { 1 };
+    #{ commands: [#{ op: "objective", key: "lightning_cannon:recovered", value: recovered }],
+       state: #{ recovered: recovered } }
+}

mods/lightning_cannon/scripts/weapon.rhai

@@ -0,0 +1,56 @@
+// The scripted discharge uses only public snapshots and checked API commands.
+// A narrow forward acquisition lane preserves aiming; later hops may go sideways.
+fn on_fire(event, state, random) {
+    if event.hostile {
+        return #{ commands: [], state: state };
+    }
+    let bursts = if state.contains("bursts") { state.bursts % 100000 + 1 } else { 1 };
+    let hits = if state.contains("hits") { state.hits } else { 0 };
+    let commands = [#{ op: "play_sound", sound: "lightning_cannon:fire" }];
+    let struck = [];
+    let from_x = event.x;
+    let from_y = event.y;
+    let damages = [32, 20, 12, 8];
+
+    for hop in 0..4 {
+        let selected = #{};
+        let nearest = 1000000;
+        for enemy in event.entities {
+            let cx = enemy.x + enemy.width / 2;
+            let cy = enemy.y + enemy.height / 2;
+            if enemy.health <= 0 || struck.contains(enemy.entity)
+                || cx < 0 || cx >= 320 || cy < 0 || cy >= 200 {
+                continue;
+            }
+            let dx = cx - from_x;
+            let dy = cy - from_y;
+            let distance = dx * dx + dy * dy;
+            let reachable = if hop == 0 {
+                abs(dx) <= 36 && dy < 0 && distance <= 180 * 180
+            } else {
+                distance <= 48 * 48
+            };
+            // Entity order provides a stable tie break for equally near targets.
+            if reachable && distance < nearest {
+                selected = #{ entity: enemy.entity, x: cx, y: cy };
+                nearest = distance;
+            }
+        }
+        if !selected.contains("entity") { break; }
+        commands.push(#{ op: "arc", x: from_x, y: from_y,
+                         to_x: selected.x, to_y: selected.y, ticks: 4 });
+        commands.push(#{ op: "damage", entity: selected.entity, amount: damages[hop] });
+        struck.push(selected.entity);
+        from_x = selected.x;
+        from_y = selected.y;
+        hits = hits % 100000 + 1;
+    }
+    if struck.len() > 0 {
+        commands.push(#{ op: "play_sound", sound: "lightning_cannon:impact" });
+    } else {
+        // A missed shot remains visible without spawning a damaging carrier.
+        commands.push(#{ op: "arc", x: event.x, y: event.y,
+                         to_x: event.x, to_y: event.y - 180, ticks: 3 });
+    }
+    #{ commands: commands, state: #{ bursts: bursts, hits: hits } }
+}