Remove C++ from language options (CVE concern)

Dropped from M3 hub, M3d, and M3g — Julia and Fortran remain
as the high-performance alternatives.

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

@@ -15,7 +15,7 @@ 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, Solidity, or C++)
+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.
 

core/docs/plans/M3d-mev-adversarial-sims.md

@@ -21,7 +21,7 @@ WENO discretization established but crypto application novel). Parameterization
 ## 3. Language & location
 TBD · `src/economy/sims/mev/`. Needs combinatorial optimization (OR-Tools for knapsack),
 continuous-time auction modeling, PDE solvers (WENO for shock-capturing in adversarial dynamics),
-and bilevel optimization (DSMFG). Julia, Fortran, or C++.
+and bilevel optimization (DSMFG). Julia or Fortran.
 
 ## 4. Does / does-not
 - **Does:** simulate Priority Gas Auctions where multiple searcher bots compete for the same

core/docs/plans/M3g-market-microstructure-sims.md

@@ -16,8 +16,7 @@ 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. C++, Fortran,
-or Julia.
+simulation, and Riccati equation solvers for optimal execution trajectories. Fortran or Julia.
 
 ## 4. Does / does-not
 - **Does:** simulate order flow across venues (DEXs and CEXs); model bid-ask spread dynamics as a