Drop Julia, assign one primary language per M3 sim spec

Ranked languages per spec by fit; took only the top pick:
- M3a (statistical): R — native stats ecosystem
- M3b (sociological): Prolog — equilibria as constraint satisfaction
- M3c (AMM): Solidity — on-chain-equivalent precision
- M3d (MEV): Fortran — dense PDE/knapsack numerics, no GC
- M3e (tokenomics): Fortran — SDE/VAR matrix loops, same toolchain as M3d
- M3f (consensus): Prolog — Markov/Nash as declarative search
- M3g (microstructure): Zig — tick-level latency, deterministic memory
- Hub: updated to reflect per-spec assignments

Julia removed project-wide: JIT startup cost and large toolchain
not justified when the project isn't going all-in on a single runtime.

core/docs/plans/M3-sims-hub.md

@@ -15,9 +15,10 @@ DESIGN-FIRST · ABSENT. Role C3; implementation C1. Mathematical foundations C4
 established); specific model parameters C1.
 
 ## 3. Language & location
-TBD · `src/economy/sims/`. Numerical computing (Julia, Octave, Fortran, R, or Solidity)
-for the simulation cores. A query facade accessible to Traders. Each sim type (M3a–M3g) may use
-a different runtime suited to its math.
+TBD · `src/economy/sims/`. Each sim type uses the runtime suited to its math: **Fortran**
+(M3d, M3e — dense numerical PDE/SDE), **Prolog** (M3b, M3f — game-theoretic equilibria),
+**R** (M3a — statistical inference), **Solidity** (M3c — on-chain precision), **Zig**
+(M3g — tick-level latency). A query facade accessible to Traders.
 
 ## 4. Does / does-not
 - **Does:** tick-advance continuously at **90:1** (1 wall-second = 90 simulated seconds)