feat(phase1): implement RNG, SampleCBD, SampleNTT modules + xsim TBs

Phase 1 complete — all 4 leaf modules verified:
- rng_sync.v: 256-bit Galois LFSR PRNG (10/10 PASS)
- sample_cbd_sync.v: CBD sampler with keccak_core PRF (2560/2560 PASS)
- sample_ntt_sync.v: SHAKE-128 rejection sampling for A matrix (1536/1536 PASS)
- xsim Verilog TBs for sha3 module (tb_sha3_xsim.v, tb_sha3_xsim_simple.v, tb_keccak_core_xsim.v)

sync_rtl/sha3/TB/xsim_run.tcl

@@ -0,0 +1,88 @@
+# xsim_run.tcl - Vivado xsim compilation and simulation script
+#
+# Compiles all SHA3 RTL sources plus testbenches and runs simulation.
+# Run from the project root: ~/Dev/mlkem/
+#
+# Prerequisites:
+#   source /opt/Xilinx/Vivado/2019.2/settings64.sh
+#
+# Usage examples:
+#   # Run simple self-checking test on sha3_top (G mode)
+#   xsim sha3_simple_sim -R
+#
+#   # Run keccak_core self-checking test
+#   xsim keccak_core_sim -R
+#
+#   # Run file-based vector test on sha3_top (requires vectors/g_basic_input.hex)
+#   xsim tb_sha3_xsim -R
+#
+#   # Full batch: compile + elaborate + run (via Tcl)
+#   xsim -runall xsim_run.tcl
+#
+#   # Or step-by-step:
+#   vivado -mode batch -source xsim_run.tcl
+
+# ================================================================
+# Configuration
+# ================================================================
+set SRC_DIR  sync_rtl/sha3
+set TB_DIR   sync_rtl/sha3/TB
+
+# ================================================================
+# Step 1: Compile all source files (xvlog)
+# ================================================================
+puts "=== Compiling RTL sources ==="
+
+# Core Keccak module (combinational round)
+xvlog -sv ${SRC_DIR}/keccak_round.v
+
+# Keccak core (24-round sequential core)
+xvlog -sv ${SRC_DIR}/keccak_core.v
+
+# SHA3 top wrapper (G/H/J modes)
+xvlog -sv ${SRC_DIR}/sha3_top.v
+
+# ================================================================
+# Step 2: Compile testbenches
+# ================================================================
+puts "=== Compiling testbenches ==="
+
+# Simple self-checking testbench (recommended for quick validation)
+xvlog -sv ${TB_DIR}/tb_sha3_xsim_simple.v
+
+# Keccak core self-checking testbench
+xvlog -sv ${TB_DIR}/tb_keccak_core_xsim.v
+
+# File-based vector testbench
+xvlog -sv ${TB_DIR}/tb_sha3_xsim.v
+
+# ================================================================
+# Step 3: Elaborate each snapshot (xelab)
+# ================================================================
+puts "=== Elaborating snapshots ==="
+
+# Simple sha3_top testbench (G mode, hardcoded vector)
+xelab tb_sha3_xsim_simple -s sha3_simple_sim
+
+# Keccak core testbench (all-zero input)
+xelab tb_keccak_core_xsim -s keccak_core_sim
+
+# File-based sha3_top testbench (reads vectors/g_basic_input.hex)
+xelab tb_sha3_xsim -s tb_sha3_xsim
+
+# ================================================================
+# Step 4: Run simulations
+# ================================================================
+puts "=== Running simple SHA3 test ==="
+xsim sha3_simple_sim -R
+
+puts ""
+puts "=== Running Keccak core test ==="
+xsim keccak_core_sim -R
+
+puts ""
+puts "=== Running file-based SHA3 test ==="
+xsim tb_sha3_xsim -R
+
+puts ""
+puts "=== All simulations complete ==="