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>

FINDINGS.md

@@ -236,6 +236,43 @@ real stockpiles.
 
 ---
 
+## Run 12 — Knowledge, mortality, and the North's soul (SPEC §5)
+
+**Built:** three skill domains (forage/woodcraft/masonry) that pay off
+(skilled hands harvest more, masons waste less) and grow by practice;
+proximity diffusion soul-calibrated by absorption × teaching-drive;
+**mortality** — the piece that makes knowledge *generational*: elders die
+at ~150–230 days, everything unshared dies with them, and a youth comes
+of age knowing almost nothing. The North's whole identity is two numbers
+(absorption 1.6, teaching 0.9) vs the South's (1.0, 0.3); the East
+teaches no one, ever.
+
+**First finding (instrumentation):** headless soaks were being
+contaminated by orphaned Godot child processes writing to later runs'
+CSVs — two files disagreeing on the final day was the tell. Fixed with a
+`StopAfterDays` clean self-terminate (no external kill, no race).
+
+**Second finding (design):** passive-only diffusion barely helped the
+North — youths spawned at the empty town centroid and worked solo, so a
+death reset a villager to roughly what they'd have self-taught anyway.
+The missing mechanic was the North's actual culture: **the young must
+seek out elders on purpose.** Added deliberate teacher-seeking for
+high-absorption souls, and youths now cradle beside the town's wisest
+elder instead of in a void.
+
+**Result:** the North leads at every checkpoint (day 150: 0.586 vs 0.477;
+final 0.972 vs 0.951) and both towns reach far higher knowledge than
+before. But the gap is modest **because a stable town approaches the
+knowledge ceiling regardless of teaching speed** — everyone eventually
+maxes out; the North just arrives sooner. Teaching culture is a
+*recovery* advantage, not an equilibrium one.
+
+**Next experiment (the real test):** a shock that kills the experts, then
+measure which town rebuilds its knowledge — the North's thesis stated as
+a falsifiable claim.
+
+---
+
 Soul layer: done and validated (runs 5–6). The expansion phase begins:
 
 1. **Towns as spatial structure**: multiple settlements with their own