Add optional wandb metrics tracking

Mirror Deep CFR training metrics to W&B via a new WandbRunTracker
wired through CompositeRunTracker; wandb is an optional extra so
default installs and runs stay unchanged. Train CLI gains
--wandb/--wandb-project/--wandb-mode/--wandb-name/--wandb-tag, and
train() now closes the tracker in a finally block so runs finalize
even on early exit.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

pyproject.toml

@@ -20,6 +20,9 @@ gui = [
     "pygame>=2.6.1",
     "pygame-gui>=0.6.14",
 ]
+wandb = [
+    "wandb>=0.17",
+]
 
 [project.scripts]
 lost-cities-classic = "coolrl_lost_cities.games.classic:main"