rename python package projected_grpo -> vgrout

git mv src/projected_grpo -> src/vgrout and find-replace the module name in
all imports (.py), `-m projected_grpo.*` invocations (justfile), and the
[project] name (pyproject; setuptools auto-discovers via where=["src"]).

Left RESEARCH_JOURNAL.md untouched: its commands/paths are dated lab notes
tied to past commits, so rewriting them would falsify provenance. Repo dir,
git remote, and absolute paths unchanged.

Verified: `import vgrout` and `python -m vgrout.train --help` load the full
graph; verify_rewards.py + verify_gate_anchor.py (both import vgrout) pass.
Full `just smoke` is blocked upstream by missing gitignored data artifacts
(out/pools/{substrate,teacher_pool}, out/vhack/*smoke*), unrelated to the rename.

scripts/plot_deploy_overlay.py

@@ -30,7 +30,7 @@ import matplotlib.pyplot as plt
 import numpy as np
 from loguru import logger
 
-from projected_grpo.figs import save_fig
+from vgrout.figs import save_fig
 
 # arm -> (display label, colour). Order = legend/bar order (baseline first).
 # Reader-facing names only -- "route2"/"grad" are internal tags. The grad-mask