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/M3a-statistical-sims.md

@@ -16,10 +16,10 @@ execution C5 (industry standard since 2001). Jump-diffusion C5 (Merton 1976). Pa
 for crypto markets C1.
 
 ## 3. Language & location
-TBD · `src/economy/sims/statistical/`. Julia, R, Fortran, or Octave for numerical computing.
-Needs efficient matrix operations, SDE solvers, and distribution sampling. Fractional Brownian
-motion generation uses spectral methods (Hosking 1984, Wood & Chan 1994) or Cholesky
-decomposition of the covariance matrix.
+TBD · `src/economy/sims/statistical/`. **R** — native statistical distribution ecosystem,
+matrix operations, and time-series libraries (GARCH, ARIMA, HMM) without wrapping external
+solvers. Fractional Brownian motion generation uses spectral methods (Hosking 1984, Wood & Chan
+1994) or Cholesky decomposition of the covariance matrix.
 
 ## 4. Does / does-not
 - **Does:** run Monte Carlo price simulations (GBM, Merton jump-diffusion, Heston stochastic