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/verify_vhack_heldout.py

@@ -8,7 +8,7 @@ Report:
   - fraction of modules with cos_align > 0  (SHOULD > 0.5)
   - mean cos_align across modules           (target > 0.2)
 
-Run: uv run python -m projected_grpo.verify_vhack_heldout
+Run: uv run python -m vgrout.verify_vhack_heldout
 """
 from __future__ import annotations
 
@@ -26,10 +26,10 @@ from safetensors.torch import save_file
 from tabulate import tabulate
 from transformers import AutoModelForCausalLM, AutoTokenizer
 
-from projected_grpo.antipasto import wrap_model_with_antipasto
-from projected_grpo.extract_vhack_grad import completion_nll, resolve_dtype
-from projected_grpo.pairs import PAIRS
-from projected_grpo.extract_vhack_grad import load_v_hack
+from vgrout.antipasto import wrap_model_with_antipasto
+from vgrout.extract_vhack_grad import completion_nll, resolve_dtype
+from vgrout.pairs import PAIRS
+from vgrout.extract_vhack_grad import load_v_hack
 
 
 CACHE_ROOT = Path("svd_cache")