fix: surface renderer errors, clean up all warnings

- Renderer init/render/shutdown errors now printed instead of silently
  swallowed with let _ =
- Auto-fixed all unused imports and variables (cargo fix)
- Zero compiler warnings

src/ai/action.rs

@@ -1,9 +1,8 @@
 use serde::{Deserialize, Serialize};
 use crate::ai::state::material_from_name;
 use crate::ai::state::parse_entity_kind;
-use crate::entity::EntityKind;
 use crate::game::Game;
-use crate::world::cell::{Cell, MaterialId};
+use crate::world::cell::Cell;
 
 #[derive(Serialize, Deserialize, Clone, Debug)]
 #[serde(tag = "type", rename_all = "snake_case")]

src/ai/protocol.rs

@@ -1,7 +1,7 @@
 use serde::{Deserialize, Serialize};
 use crate::ai::action::AiAction;
 use crate::ai::session::GameSession;
-use crate::ai::scenario::{run_scenario, Scenario, format_results, load_scenario, run_all_scenarios};
+use crate::ai::scenario::{run_scenario, format_results, load_scenario, run_all_scenarios};
 use crate::ai::state::GameState;
 use std::io::{self, BufRead, Write};
 

src/ai/replay.rs

@@ -1,7 +1,6 @@
 use serde::{Deserialize, Serialize};
 use crate::ai::action::AiAction;
 use crate::ai::session::GameSession;
-use std::io::Write;
 
 #[derive(Serialize, Deserialize, Clone, Debug)]
 pub struct ReplayRecording {

src/ai/scenario.rs

@@ -1,7 +1,7 @@
 use serde::{Deserialize, Serialize};
 use crate::ai::action::AiAction;
 use crate::ai::session::GameSession;
-use crate::ai::state::{GameState, material_from_name};
+use crate::ai::state::GameState;
 
 #[derive(Serialize, Deserialize, Clone, Debug)]
 pub struct Scenario {

src/game.rs

@@ -71,7 +71,7 @@ impl Game {
         // Water pool (left side)
         let water_x = 40;
         let water_surface = (h as i32 - 3) - ((water_x as f32 * 0.1).sin() * 5.0) as i32;
-        let water_surface = water_surface.max(10).min(h as i32 - 3);
+        let _water_surface = water_surface.max(10).min(h as i32 - 3);
         for x in water_x - 12..=water_x + 12 {
             let s = (h as i32 - 3) - ((x as f32 * 0.1).sin() * 5.0) as i32;
             let s = s.max(10).min(h as i32 - 3);

src/world/cellular.rs

@@ -1,6 +1,5 @@
 use crate::world::cell::{Cell, MaterialId};
 use crate::world::grid::Grid;
-use crate::world::material::MaterialRegistry;
 
 pub struct CellularAutomaton {
     tick: u64,