Migrate Amazon Connect TEI study to the Mercury Notebook Pattern

studies/202602_AmazonConnect -> studies/202602_TEI_Amazon_Connect,
rebuilt as pattern Variant 4 (TEI composite reproduction):

- teicalc/ self-contained engine (stdlib-only): Forrester's tables as
  the never-edited verbatim anchor, NPV/ROI/payback + risk adjustment
  transplanted from core/calculations, ClientDrivers overlay (contacts/
  agents/fixed driver map, growth re-base, identity at composite scale),
  scenario stress with core-identical semantics
- one deliverable notebook (business_case.ipynb): widget-pair sidebar
  drivers, published-vs-overlay KPI columns, cash-flow/waterfall/scenario
  charts, verification gate, backstage JSON data appendix
- gate + tests reproduce the published totals within PDF rounding:
  NPV $78.7M / ROI 342% / payback <6 months (engine $78,713,492 /
  342.48% / 0.7 months); 27 study tests, headless nbconvert green,
  stage simulation leak-free, exports carry the appendix
- old Athena workflow (00_provision..04_export, config.py, seed_data.py)
  deleted; git history preserves it; root test fixture repointed to
  teicalc.anchor
- docs: study README rewritten; root README points new studies at
  template/MercuryNotebook; pattern doc stale ctm-token-calculator paths
  now cite studies/202607_CTM_GenesysCX; Variant 4 cites this study as
  its realized reference

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/conftest.py

@@ -22,11 +22,16 @@ def _env(monkeypatch):
 
 @pytest.fixture
 def amazon_connect_seed():
-    """Load the Amazon Connect study's seed data."""
-    sys.path.insert(0, str(ROOT / "studies" / "202602_AmazonConnect"))
+    """Load the Amazon Connect study's verbatim anchor (post-migration the
+    study is self-contained; teicalc is stdlib-only, so importing it here
+    needs no study venv — the row shape matches the old seed_data)."""
+    from types import SimpleNamespace
+
+    sys.path.insert(0, str(ROOT / "studies" / "202602_TEI_Amazon_Connect"))
     try:
-        import seed_data  # type: ignore[import-not-found]
-        return seed_data
+        from teicalc import anchor  # type: ignore[import-not-found]
+        return SimpleNamespace(BENEFITS=anchor.BENEFITS_VERBATIM,
+                               COSTS=anchor.COSTS_VERBATIM)
     finally:
         # Leave the path alone — many tests will use the seed
         pass