fix(ui): restore staged loading progress

Correct raw 1000:531e's Pascal-order BitBlt to destination (202,328), height 13, and width (stage-1)*7 from original DAT994. Render stages 2 through 35 over DAT995, add deterministic loading screenshots, and update the C harness and evidence ledger for the corrected 237x13 source.

Test Plan:
- bash original/tools/test_reconstructed_c.sh
- python3 original/tools/audit_reconstruction.py --require-complete
- cargo test --all-targets
- cargo clippy --all-targets --all-features -- -D warnings
- rumdl check original/C_RECONSTRUCTION_FINAL_AUDIT.md tdkpin-rs/CHANGELOG.md tdkpin-rs/RECONSTRUCTION.md tdkpin-rs/README.md
- cargo run --quiet -- --simulate loading --at 0.55 --screenshot /tmp/tdkpin-loading-mid.png
- git diff --check

tdkpin-rs/src/simulation.rs

@@ -13,6 +13,7 @@ const MAX_SIMULATION_STEPS: u64 = 72_000;
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum Scenario {
+    Loading,
     Attract,
     Autoplay,
     Launcher,
@@ -28,6 +29,7 @@ pub enum Scenario {
 impl Scenario {
     pub const fn name(self) -> &'static str {
         match self {
+            Self::Loading => "loading",
             Self::Attract => "attract",
             Self::Autoplay => "autoplay",
             Self::Launcher => "launcher",
@@ -47,7 +49,8 @@ impl Scenario {
             Self::Claw6 => Some(6),
             Self::Claw7 => Some(7),
             Self::Claw18 => Some(18),
-            Self::Attract
+            Self::Loading
+            | Self::Attract
             | Self::Autoplay
             | Self::Launcher
             | Self::Flippers
@@ -62,6 +65,7 @@ impl FromStr for Scenario {
 
     fn from_str(value: &str) -> Result<Self, Self::Err> {
         match value {
+            "loading" => Ok(Self::Loading),
             "attract" => Ok(Self::Attract),
             "autoplay" => Ok(Self::Autoplay),
             "launcher" => Ok(Self::Launcher),
@@ -73,7 +77,7 @@ impl FromStr for Scenario {
             "claw-7" => Ok(Self::Claw7),
             "claw-18" => Ok(Self::Claw18),
             _ => Err(format!(
-                "unknown scenario {value:?}; expected attract, autoplay, launcher, flippers, panel, targets, claw-1, claw-6, claw-7, or claw-18"
+                "unknown scenario {value:?}; expected loading, attract, autoplay, launcher, flippers, panel, targets, claw-1, claw-6, claw-7, or claw-18"
             )),
         }
     }
@@ -157,7 +161,7 @@ fn seconds_to_step(value: &str) -> Result<u64, String> {
 }
 
 pub const fn usage() -> &'static str {
-    "Usage:\n  tdkpin-rs\n  tdkpin-rs --simulate SCENARIO [--at SECONDS | --step N] [--screenshot FILE.png] [--trace FILE.json] [--seed N]\n\nScenarios: attract, autoplay, launcher, flippers, panel, targets, claw-1, claw-6, claw-7, claw-18"
+    "Usage:\n  tdkpin-rs\n  tdkpin-rs --simulate SCENARIO [--at SECONDS | --step N] [--screenshot FILE.png] [--trace FILE.json] [--seed N]\n\nScenarios: loading, attract, autoplay, launcher, flippers, panel, targets, claw-1, claw-6, claw-7, claw-18"
 }
 
 #[derive(Debug, Serialize, PartialEq)]
@@ -238,7 +242,7 @@ impl Simulation {
             } else {
                 controls_for(self.scenario, self.step)
             };
-            let events = if self.scenario == Scenario::Attract {
+            let events = if matches!(self.scenario, Scenario::Loading | Scenario::Attract) {
                 Vec::new()
             } else {
                 self.game.update(SIMULATION_DT, 3, controls)
@@ -332,7 +336,7 @@ impl Simulation {
 
 fn controls_for(scenario: Scenario, step: u64) -> Controls {
     match scenario {
-        Scenario::Attract => Controls::default(),
+        Scenario::Loading | Scenario::Attract => Controls::default(),
         Scenario::Autoplay => unreachable!("autoplay controls need mutable simulation state"),
         Scenario::Launcher => Controls {
             launch_down: step < u64::from(SIMULATION_HZ),