cleanup: delete dead delta_S machinery (PiSSA->lora2r leftovers)

Off the live lora2r path; removed with vhack.py (commit 4120d75):
- proj.py: drop project_delta_S_grad/_project_one_module/mean_cos_pre_from_grads/
  _hackward_cos (no live importer; train.py uses only per_token_logps).
- verify_science_invariants: test pairset_sha256's content gate directly (drops the
  load_v_hack vehicle + fake delta_S wrapper fixture).
- extract_vhack_grad: import pairset_sha256 from .pairs (was re-exported via vhack).
- tablelog/figs: stale 'delta_S grads'/'knob' comments -> A/B grads.
Smoke + verify_science_invariants green; no delta_S left in live code.

Co-Authored-By: Claudypoo <288921227+claudypoo@users.noreply.github.com>

scripts/verify_science_invariants.py

@@ -6,14 +6,12 @@ import json
 import tempfile
 from pathlib import Path
 
-import torch
 from loguru import logger
-from safetensors.torch import save_file
 from tabulate import tabulate
 
 from vgrout.data import DATA, RH_HINT_REPLACE_FROM, load_problems
 from vgrout.eval import load_eval_splits
-from vgrout.vhack import load_v_hack, pairset_sha256
+from vgrout.pairs import load_pairs, pairset_sha256
 
 
 def _must_raise(fn) -> bool:
@@ -29,20 +27,45 @@ def main() -> int:
     with tempfile.TemporaryDirectory() as td:
         tmp = Path(td)
 
-        pairs_path = tmp / "pairs.json"
-        pairs_path.write_text('[{"prompt":"p","hack":"h","clean":"c"}]\n')
-        vhack_path = tmp / "vhack.safetensors"
-        dtype = "bf16" if torch.cuda.is_available() else "fp32"
-        save_file(
-            {"module": torch.tensor([[1.0, 0.0, 0.0]]), "_sv/module": torch.tensor([1.0])},
-            str(vhack_path),
-            metadata={"model": "test", "dtype": dtype, "pairs_sha256": pairset_sha256(pairs_path)},
+        pairs_path = tmp / "pairs.md"
+        pairs_path.write_text(
+            "## tiny\n\n### p\n\n#### Prompt\n`````text\np\n`````\n\n"
+            "#### Hack\n`````text\nh\n`````\n\n#### Clean\n`````text\nc\n`````\n\n"
+            "## unrelated\n\n### q\n\n#### Prompt\n`````text\nq\n`````\n\n"
+            "#### Hack\n`````text\nx\n`````\n\n#### Clean\n`````text\ny\n`````\n"
         )
-        wrappers = {"module": {"delta_S": torch.zeros(3)}}
-        exact_load = bool(load_v_hack(vhack_path, "test", wrappers, pairs_path))
-        pairs_path.write_text(pairs_path.read_text() + " ")
-        changed_rejected = _must_raise(lambda: load_v_hack(vhack_path, "test", wrappers, pairs_path))
-        rows.append({"invariant": "v_hack pair bytes", "success": exact_load and changed_rejected})
+        # Pairsets are content-addressed by the SELECTED section's bytes (pairset_sha256):
+        # an edit elsewhere in the file must not change the hash; an edit inside the
+        # selected section must. This is what gates a stale extracted direction.
+        pairs_ref = Path(f"{pairs_path}#tiny")
+        selected_hash = pairset_sha256(pairs_ref)
+        pairs_path.write_text(pairs_path.read_text().replace("\nx\n", "\nother changed\n"))
+        unrelated_ignored = pairset_sha256(pairs_ref) == selected_hash
+        pairs_path.write_text(pairs_path.read_text().replace("\nh\n", "\nchanged\n"))
+        selected_changed = pairset_sha256(pairs_ref) != selected_hash
+        missing_rejected = _must_raise(lambda: load_pairs(Path(f"{pairs_path}#missing")))
+        rows.append({
+            "invariant": "selected Markdown pair bytes",
+            "success": bool(selected_hash) and unrelated_ignored and selected_changed and missing_rejected,
+        })
+
+        malformed = tmp / "malformed.md"
+        malformed.write_text(
+            "## x\n\n### duplicate\n\n#### Prompt\n`````text\np\n`````\n\n"
+            "#### Prompt\n`````text\np2\n`````\n\n#### Hack\n`````text\nh\n`````\n\n"
+            "#### Clean\n`````text\nc\n`````\n"
+        )
+        rows.append({
+            "invariant": "malformed Markdown fails",
+            "success": _must_raise(lambda: load_pairs(Path(f"{malformed}#x"))),
+        })
+
+        real_pairsets_ok = (
+            len(load_pairs(Path("docs/personas/hack_pairs.md#mechanism-authored"))) == 11
+            and len(load_pairs(Path("docs/personas/pair_diagnostics.md#null-vampire"))) == 12
+            and len(load_pairs(Path("out/pairsets/prog_wide_clean.json"))) == 8
+        )
+        rows.append({"invariant": "authored/control/generated pairsets load", "success": real_pairsets_ok})
 
         source = json.loads(DATA.read_text().splitlines()[0])
         missing = json.loads(json.dumps(source))