feat(*): Add idempotent tmux-based training scripts for the Linux box

TRAINING_LINUX.md

@@ -62,25 +62,31 @@ mini — a 20M-step run in ~4 h. Doubling fps halves that.
 
 ## Run training
 
-`run_training.sh <experiment> [train.py args...]` wraps the whole cycle:
+One command does everything (needs `tmux`: `sudo apt install tmux`):
-`git pull` → train → export the policy JSON → commit and push checkpoints,
-logs, and the exported bot. Run it inside `tmux`/`screen` so an SSH
-disconnect doesn't kill training. Ctrl-C is safe: the trainer writes
-`final.zip` on the way out, and the script still exports, commits, and
-pushes what it has.
-
-Fresh run:
 
 ```bash
 cd ~/ai-training/CosmicClash/training
-./run_training.sh run03 --timesteps 20000000 --n-parallel 14 --speedup 24
+./start_training.sh run03 --timesteps 20000000 --n-parallel 14 --speedup 24
 ```
 
+`start_training.sh` launches a detached tmux session with two windows —
+**training survives SSH disconnects** — and prints the dashboard URL:
+
+- `train` runs `run_training.sh`: `git pull` → train → export the policy
+  JSON → commit and push checkpoints, logs, and the exported bot;
+- `dashboard` serves TensorBoard on `0.0.0.0:6006` for the whole network
+  (reused if one is already running).
+
+Re-running `start_training.sh` while a session exists just attaches you to
+it (detach again with `Ctrl-B` then `D`) — it will never start a second
+trainer. To stop training, attach and Ctrl-C: the trainer writes `final.zip`
+on the way out and the script still exports, commits, and pushes what it has.
+
 Resuming a previous policy (continues its timestep counter; `--timesteps` is
 *additional* steps). Lessons from run01/run02 hard-coded into flags:
 
 ```bash
-./run_training.sh run03 --timesteps 20000000 --n-parallel 14 --speedup 24 \
+./start_training.sh run03 --timesteps 20000000 --n-parallel 14 --speedup 24 \
     --resume checkpoints/run02/final.zip --ent-coef 0.001 --reset-std 0.3
 ```
 
@@ -108,16 +114,11 @@ guarantee that training is never lost with a machine.
 
 ## Dashboard over the network
 
-On the Linux box, bind TensorBoard to all interfaces instead of localhost:
+`start_training.sh` already serves TensorBoard on all interfaces — browse to
-
+the URL it prints (`http://10.0.0.20:6006`) from the Mac or anything on
-```bash
+the LAN.
-cd ~/ai-training/CosmicClash/training
-.venv/bin/tensorboard --logdir logs --host 0.0.0.0 --port 6006
-```
-
-Then from the Mac (or anything on the LAN): `http://<linux-box-hostname>:6006`.
 
 - If `ufw` is active on the box: `sudo ufw allow 6006/tcp`.
 - If you'd rather not open a port, tunnel instead:
-  `ssh -L 6006:localhost:6006 <linux-box>` from the Mac, then browse
+  `ssh -L 6006:localhost:6006 10.0.0.20` from the Mac, then browse
   `http://localhost:6006`.

training/start_training.sh

@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+# The one command to run on the training box. Starts, fully detached from
+# your SSH session (safe to disconnect any time):
+#
+#   window "train":     run_training.sh — git pull, train, export, commit+push
+#   window "dashboard": TensorBoard on 0.0.0.0:6006 (LAN-accessible)
+#
+# Idempotent: if a training session already exists it attaches to it instead
+# of starting a second trainer, and an already-running dashboard is reused.
+#
+# Usage: ./start_training.sh <experiment> [train.py args...]
+# e.g.:  ./start_training.sh run02 --timesteps 20000000 --n-parallel 14 --speedup 16 \
+#            --resume checkpoints/run01/final.zip --ent-coef 0.001 --reset-std 0.3
+set -euo pipefail
+cd "$(dirname "$0")"
+
+SESSION="cosmic-train"
+TB_PORT=6006
+
+command -v tmux >/dev/null 2>&1 || { echo "tmux is required: sudo apt install tmux" >&2; exit 1; }
+
+if tmux has-session -t "$SESSION" 2>/dev/null; then
+    echo "Session '$SESSION' already running — attaching (detach with Ctrl-B then D)."
+    exec tmux attach -t "$SESSION"
+fi
+
+EXP="${1:?usage: start_training.sh <experiment> [train.py args...]}"
+
+# Keep the window open after the run so its output and exit status stay
+# readable; the results themselves are already safe in git by then.
+tmux new-session -d -s "$SESSION" -n train \
+    "./run_training.sh $*; echo; echo '=== run_training.sh exited — results are committed; press Enter to close ==='; read"
+
+# Dashboard, unless something (a previous session) is already serving it
+if ! (exec 3<>"/dev/tcp/127.0.0.1/$TB_PORT") 2>/dev/null; then
+    tmux new-window -d -t "$SESSION" -n dashboard \
+        ".venv/bin/tensorboard --logdir logs --host 0.0.0.0 --port $TB_PORT"
+fi
+
+IP=$(hostname -I 2>/dev/null | awk '{print $1}')
+echo "Training '$EXP' started in tmux session '$SESSION' — SSH disconnects won't touch it."
+echo "  watch it:   tmux attach -t $SESSION   (detach again with Ctrl-B then D)"
+echo "  dashboard:  http://${IP:-<this-box>}:$TB_PORT"