fix(simulation): address PR #81 review — critical and high-priority issues

Critical fixes:
- storyteller: replace .expect() with guard + log in activation_pass (Hoshe #1)
- content/loader: validate inverted tile_bounds before iteration (Hoshe #C)
- save_io: persist ActivationState on save/load (Tyre #7)

High-priority fixes:
- storyteller: f64 intermediate for observation_time_ticks scoring (Hoshe #A)
- storyteller: deduplicate copresent entities before scoring (Hoshe #B)
- storyteller: skip activation_pass at tick 0 (Hoshe #G)
- storyteller: explicit .before(advance_tick) ordering (Tyre #9)
- save_state: insert EngagementRecord on NPC deserialize (Tyre #10)
- save_io: reset TriangleActivatedQueue + MovementHistoryBuffer on load (Tyre #8)
- debug: validate teleport target walkability (Hoshe #E)
- debug: reject SkipToContamination when tick past delay (Hoshe #F)
- debug: DebugEnabled defaults to cfg!(debug_assertions) (Hoshe #3)
- debug: log when response overwritten (Hoshe #2)
- content/loader: error on tile dimension mismatch (Hoshe #5)
- content/types: DistrictMeta.description optional (Hoshe #D)
- types: version docs updated to v18 (Tyre #1, #2, #3)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/content/loader.rs

@@ -377,29 +377,43 @@ fn apply_location_tiles(location: &Location, walkability: &mut WalkabilityMap) -
         return false;
     };
 
+    // Guard: inverted bounds cause (y_max - y_min) to be negative, which wraps to
+    // ~18 quintillion when cast to usize, silently writing tiles at garbage positions.
+    if bounds.x_min > bounds.x_max || bounds.y_min > bounds.y_max {
+        tracing::error!(
+            "Location '{}': inverted tile_bounds (x: {}..={}, y: {}..={}), skipping",
+            location.canonical_id,
+            bounds.x_min, bounds.x_max,
+            bounds.y_min, bounds.y_max,
+        );
+        return false;
+    }
+
     let expected_height = (bounds.y_max - bounds.y_min + 1) as usize;
     let expected_width = (bounds.x_max - bounds.x_min + 1) as usize;
 
     if tiles.len() != expected_height {
-        tracing::warn!(
-            "Location '{}': tile row count {} != expected height {} (from tile_bounds)",
+        tracing::error!(
+            "Location '{}': tile row count {} != expected height {} (from tile_bounds) — skipping to prevent walkability holes",
             location.canonical_id,
             tiles.len(),
             expected_height,
         );
+        return false;
     }
 
     for (row_idx, row) in tiles.iter().enumerate() {
         let y = bounds.y_min + row_idx as i32;
 
         if row.len() != expected_width {
-            tracing::warn!(
-                "Location '{}' row {}: length {} != expected width {}",
+            tracing::error!(
+                "Location '{}' row {}: length {} != expected width {} — skipping row to prevent walkability holes",
                 location.canonical_id,
                 row_idx,
                 row.len(),
                 expected_width,
             );
+            continue;
         }
 
         for (col_idx, ch) in row.chars().enumerate() {