Run 12: knowledge system, mortality, and the North's generational soul

SPEC §5 built: three skill domains (forage/woodcraft/masonry) that pay
off and grow by practice; proximity diffusion soul-calibrated by
absorption x teaching-drive; and mortality - the piece that makes
knowledge generational. Elders die (~150-230 days), everything unshared
dies with them, a youth comes of age near knowing nothing. North soul
(absorption 1.6, teaching 0.9) vs South (1.0, 0.3); East teaches no one.

Two findings: (1) headless soaks were contaminated by orphaned child
processes writing later runs' CSVs - fixed with StopAfterDays clean
self-terminate; (2) passive diffusion barely helped - the North's real
culture is the young seeking elders on purpose, so added deliberate
teacher-seeking and youths now cradle beside the wisest elder. North
now leads knowledge at every checkpoint, but a stable town approaches
the ceiling regardless, so teaching is a recovery advantage not an
equilibrium one. The crisis-recovery experiment is the real test, noted
in FINDINGS as next.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

scripts/GameManager.cs

@@ -36,6 +36,11 @@ public partial class GameManager : Node2D
     [Export(PropertyHint.Range, "1,2000,1")]
     public float TicksPerRealSecond = 20f;   // sim speed; ~1500 ≈ one day/sec for soaks
 
+    /// <summary>Auto-quit after this many days (0 = run forever). Set for
+    /// headless soaks so runs self-terminate cleanly — no external kill, no
+    /// orphaned process racing the next run's CSV writes.</summary>
+    [Export] public int StopAfterDays = 0;
+
     public World World { get; private set; } = null!;
     public List<Npc> Npcs { get; } = new();
     public List<Building> Buildings { get; } = new();
@@ -91,14 +96,20 @@ public partial class GameManager : Node2D
         {
             for (int i = 0; i < count; i++)
             {
-                Npcs.Add(new Npc
+                var npc = new Npc
                 {
                     Name = $"{prefix}_{(char)('A' + Npcs.Count % 26)}{(Npcs.Count >= 26 ? Npcs.Count.ToString() : "")}",
                     HomeTown = town,
                     Soul = soul,
                     PersonalityModifier = (float)(rng.NextDouble() * 0.4 - 0.2),
                     Position = center + new Vector2(rng.Next(-12, 13), rng.Next(-12, 13)),
-                });
+                    // Staggered ages so the founding generation doesn't die
+                    // in one terrible week.
+                    AgeDays = rng.Next(0, 100),
+                    LifeExpectancyDays = 150 + rng.Next(0, 80),
+                };
+                npc.Know.Capacity = 1.0f + (float)rng.NextDouble();
+                Npcs.Add(npc);
             }
         }
 
@@ -198,6 +209,65 @@ public partial class GameManager : Node2D
         }
     }
 
+    // --- Mortality: generations end, and what wasn't passed on ends too --
+
+    public int DeathsToday { get; set; }
+    private int _bornCount;
+
+    private void TickMortality()
+    {
+        var dying = new List<Npc>();
+        foreach (var npc in Npcs)
+        {
+            npc.AgeDays += 1f;
+            if (npc.AgeDays >= npc.LifeExpectancyDays)
+                dying.Add(npc);
+        }
+
+        var rng = new System.Random(Seed + (int)TotalTicks);
+        foreach (var dead in Npcs.ToArray())
+        {
+            if (!dying.Contains(dead)) continue;
+            Npcs.Remove(dead);
+            DeathsToday++;
+
+            // Everything unshared dies with them: skills, memories, echoes.
+            // What survives is what they taught, built, and stored.
+            foreach (var other in Npcs)
+                other.ForgetPerson(dead);
+
+            // A youth comes of age in the same town, same culture, knowing
+            // almost nothing — but raised among the living, not in a void.
+            // They spawn beside the town's wisest elder, so the young begin
+            // life within reach of what the community still remembers. The
+            // town's knowledge is only what its living carry — but the young
+            // start where that knowledge is.
+            _bornCount++;
+            Npc? elder = null;
+            float bestKnow = -1f;
+            foreach (var other in Npcs)
+                if (other.HomeTown == dead.HomeTown && other.Know.Total > bestKnow)
+                    { bestKnow = other.Know.Total; elder = other; }
+            Vector2 cradle = elder?.Position ?? TownCentroid(dead.HomeTown);
+
+            var youth = new Npc
+            {
+                Name = $"{dead.HomeTown}_{(char)('A' + _bornCount % 26)}{_bornCount + 25}",
+                HomeTown = dead.HomeTown,
+                Soul = dead.Soul,     // raised in the culture that raised them
+                PersonalityModifier = (float)(rng.NextDouble() * 0.4 - 0.2),
+                Position = cradle + new Vector2(rng.Next(-4, 5), rng.Next(-4, 5)),
+                AgeDays = 0f,
+                LifeExpectancyDays = 150 + rng.Next(0, 80),
+            };
+            youth.Know.Capacity = 1.0f + (float)rng.NextDouble();
+            Npcs.Add(youth);
+
+            GD.Print($"[Passing] day {Day}: {dead.Name} dies at {dead.AgeDays:0} days " +
+                     $"(knowledge {dead.Know.Total:0.00} lost); {youth.Name} comes of age.");
+        }
+    }
+
     /// <summary>Where the community's feet actually are — new communal
     /// buildings are founded here, not at a scripted town center.</summary>
     public Vector2 CommunityCentroid()
@@ -224,9 +294,16 @@ public partial class GameManager : Node2D
                 building.DailyUpkeep();
             foreach (var npc in Npcs)
                 npc.FadeEchoes(0.005f);
+            TickMortality();
             StatsLogger.LogDay(this);
             if (Day % 10 == 0)
                 GD.Print($"[WorldSim] Day {Day} complete.");
+
+            if (StopAfterDays > 0 && Day >= StopAfterDays)
+            {
+                GD.Print($"[WorldSim] Reached day {Day} — stopping.");
+                GetTree().Quit();
+            }
         }
     }
 }