CI R1: add missing-notebook skip guard + tighten generic anchors

CI AI review on #439 R1:

P1: tests/_tutorial_drift.py read docs/tutorials/*.ipynb
unconditionally, but the Rust-test CI matrix copies only tests/ to
/tmp/tests and runs pytest there (no docs/), so the new tests would
FileNotFoundError instead of skipping cleanly. Added pytest.skip()
guard in _read_notebook() matching the repo convention used in
test_notebook_md_extract.py and test_nprobust_port.py.

P3: tightened two generic anchors that could false-pass:
- T21 'WAS' (matches many incidental occurrences) -> 'target = `WAS`'
  (the exact paper-step-1 phrasing, single occurrence).
- T20 'median' + '$25K' (split, can both pass independently even if
  the sentence drifts) -> 'median ~$25K' (the exact tilde-prefixed
  phrase from the design-fit narrative).

Author: igerber

tests/_tutorial_drift.py

@@ -20,8 +20,24 @@
 
 
 def _read_notebook(nb_relpath: str) -> dict:
-    """Load a notebook by repo-relative path (e.g. ``docs/tutorials/X.ipynb``)."""
+    """Load a notebook by repo-relative path (e.g. ``docs/tutorials/X.ipynb``).
+
+    Skips the calling test via ``pytest.skip(...)`` when the notebook file
+    is not present. The Rust-test CI job (and the isolated-install job)
+    copies only ``tests/`` to ``/tmp/tests`` and runs from there, without
+    ``docs/`` available. The repo convention is to skip cleanly when
+    artifacts are absent rather than fail (see e.g.
+    ``tests/test_notebook_md_extract.py`` and ``tests/test_nprobust_port.py``).
+    """
+    import pytest
+
     nb_path = Path(__file__).resolve().parents[1] / nb_relpath
+    if not nb_path.exists():
+        pytest.skip(
+            f"Notebook {nb_relpath!r} not available in this CI environment "
+            "(isolated-install job copies only tests/, not docs/); "
+            "rendered-surface cross-check requires a full repo checkout."
+        )
     return json.loads(nb_path.read_text())
 
 

tests/test_t20_had_brand_campaign_drift.py

@@ -314,8 +314,9 @@ def test_notebook_quotes_match_pinned_constants():
         # Placebo-magnitude prose claim (locked analytically above by
         # test_event_study_pre_atts_near_zero with the ±0.1 envelope).
         "±0.06",
-        # Sample summary in the design-fit narrative.
-        "median",
-        "$25K",
+        # Sample-summary phrase in the design-fit narrative. Use the
+        # exact tilde-prefixed form so a future drift in the sentence
+        # (e.g. "median around $25K") would surface here.
+        "median ~$25K",
     ]
     assert_quotes_in_rendered(T20_NOTEBOOK, expected_quotes, surface="rendered")

tests/test_t21_had_pretest_workflow_drift.py

@@ -434,7 +434,10 @@ def test_notebook_quotes_match_pinned_constants():
         "0.2899",  # Yatchew side-panel null=mean_independence p-value
         # Design auto-detect outcome (also pinned by overall-path tests).
         "continuous_at_zero",
-        "WAS",
+        # Use the exact paper-step-1 phrasing with target=`WAS` so we
+        # don't false-pass on the many incidental occurrences of "WAS"
+        # elsewhere in the prose.
+        "target = `WAS`",
         # Overall Yatchew p-value (analytical short-circuit on this DGP).
         "1.0000",
         # Overall Yatchew sigma2_lin in the rendered output.