fix(tb): fix Vivado 2019.2 compatibility and add run_tb.sh

- Replace -include_dirs . with -i . (Vivado 2019.2 syntax)
- Add --timescale 1ns/1ps to all xelab commands
- Add LD_PRELOAD comment for ncurses compatibility
- Add run_tb.sh convenience script
  Usage: ./run_tb.sh mod_add
         ./run_tb.sh --list
- Update spec with Vivado 2019.2 compatibility notes

.trellis/spec/rtl/xsim-tb-conventions.md

@@ -144,26 +144,54 @@ d00d00
 
 Width `W` must evenly contain all packed fields. Use padding bits to align to hex-char boundaries (multiples of 4 bits).
 
+## Running Testbenches
+
+### Quick Run
+```bash
+# List available modules
+./run_tb.sh --list
+
+# Run a specific module
+./run_tb.sh mod_add
+```
+
+### Manual Run
+```bash
+source /opt/Xilinx/Vivado/2019.2/settings64.sh
+export LD_PRELOAD=/usr/lib64/libtinfo.so.5  # required for Vivado 2019.2 on modern Linux
+cd ~/Dev/mlkem
+vivado -mode batch -source sync_rtl/mod_add/TB/xsim_run.tcl
+```
+
+### Vivado 2019.2 Compatibility Notes
+- **Include flag**: Use `-i .` (not `-include_dirs .` — that's Vivado 2020+)
+- **ncurses fix**: `export LD_PRELOAD=/usr/lib64/libtinfo.so.5` resolves `_nc_tiparm` symbol error from bundled LLVM 3.1
+- **Timescale**: Always pass `--timescale 1ns/1ps` to `xelab` (RTL modules may lack `timescale directives)
+
 ## xsim_run.tcl
 
 ```tcl
+# NOTE: On some systems, you may need:
+#   export LD_PRELOAD=/usr/lib64/libtinfo.so.5
+
 # Compile RTL dependencies (order matters for submodule hierarchy)
-xvlog -sv -include_dirs . <rtl_dir>/<submodule>.v
-xvlog -sv -include_dirs . <rtl_dir>/<dut>.v
+xvlog -sv -i . <rtl_dir>/<submodule>.v
+xvlog -sv -i . <rtl_dir>/<dut>.v
 
 # Compile testbench
 xvlog -sv <tb_dir>/tb_<module>_xsim.v
 
 # Elaborate
-xelab tb_<module>_xsim -s <snapshot>
+xelab tb_<module>_xsim -s <snapshot> --timescale 1ns/1ps
 
 # Run
 xsim <snapshot> -R
 ```
 
 ### CRITICAL: Include Directories
-- If ANY compiled file uses `` `include "sync_rtl/common/defines.vh" `` (or any relative include), add `-include_dirs .` to ALL `xvlog` invocations in that TCL
-- This ensures Vivado resolves paths relative to the project root
+- If ANY compiled file uses `` `include "sync_rtl/common/defines.vh" `` (or any relative include), add `-i .` to ALL `xvlog` invocations in that TCL
+- **Vivado 2019.2**: Use `-i .` (single dash)
+- **Vivado 2020+**: Use `-include_dirs .` (single or double dash)
 
 ## gen_vectors.py