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/M3g-market-microstructure-sims.md

@@ -15,8 +15,9 @@ optimal execution C5 (industry standard since 2001; crypto adaptations validated
 Kurz CMC thesis). DEX-specific microstructure C2 (emerging). Implementation C1.
 
 ## 3. Language & location
-TBD · `src/economy/sims/microstructure/`. Needs high-frequency data handling, event-driven
-simulation, and Riccati equation solvers for optimal execution trajectories. Fortran or Julia.
+TBD · `src/economy/sims/microstructure/`. **Zig** — tick-level event-driven simulation with
+deterministic memory layout, no GC pauses, and sub-microsecond latency for Riccati solvers and
+order-book state updates; comptime generics eliminate runtime dispatch on hot paths.
 
 ## 4. Does / does-not
 - **Does:** simulate order flow across venues (DEXs and CEXs); model bid-ask spread dynamics as a