Migrate Genesys CX Cloud TEI study to the pattern; retire Streamlit app

studies/202512_GenesysCX -> studies/202512_TEI_Genesys_CX_Cloud,
rebuilt as pattern Variant 4 (TEI composite reproduction):

- teicalc/ self-contained engine: Forrester's tables as the never-edited
  verbatim anchor (incl. the p.14 typo note and the $0 AI-token line),
  generic model/scenarios/staging carried over from the Amazon Connect
  study, ClientDrivers overlay (agents / weekly interactions / revenue,
  flat composite so no growth re-base) with ai_tokens_annual as a direct
  input for the token line the published study models at $0
- one deliverable notebook (business_case.ipynb): widget-pair sidebar
  drivers incl. the AI-token price, published-vs-overlay KPI columns,
  cash-flow/waterfall/scenario charts, verification gate, backstage JSON
  data appendix
- gate + tests reproduce the published totals within $2: NPV $10.8M /
  ROI 266% (engine $10,783,466 / 265.79%; payback 3.3 months, not
  headlined in the PDF); 29 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,
  PALLADIUM_GENESYSCX_* keys, ATHENA_EXPECTED reconciliation) deleted;
  git history preserves it

With the last legacy study migrated, the retirement lands too:
- app/ (Streamlit UI) and core/notebook_helpers deleted; nothing else
  imported them
- streamlit stripped from pyproject extras, requirements.txt, Makefile;
  .env.example reduced to the Athena keys; 00_setup.ipynb and
  core/bootstrap.py repointed at the pattern studies
- root README reworked: self-contained studies + slim core/ Athena
  toolkit (tei_client, calculations, export, cli)

All suites green: Genesys 29, Amazon Connect 27, CTM 55, template 7,
root 58.

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

studies/202512_TEI_Genesys_CX_Cloud/scripts/export_report.py

@@ -0,0 +1,47 @@
+"""Export the deliverable notebooks as LLM-readable report sources.
+
+Executes each notebook fresh (widget defaults — or whatever defaults you edit in),
+then writes both formats to exports/:
+
+  exports/<notebook>.html  — human-reviewable, tables render
+  exports/<notebook>.md    — leanest LLM input
+
+Plotly figures export as JavaScript an LLM cannot read; each notebook's
+machine-readable appendix section carries every number behind them.
+
+Run from the project root:  python scripts/export_report.py [name-filter]
+An optional argument exports only notebooks whose filename contains it.
+"""
+from __future__ import annotations
+
+import subprocess
+import sys
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parent.parent
+NOTEBOOKS = [
+    ROOT / "notebooks" / "business_case.ipynb",
+]
+EXPORTS = ROOT / "exports"
+
+
+def main() -> None:
+    picked = [nb for nb in NOTEBOOKS
+              if len(sys.argv) < 2 or sys.argv[1] in nb.name]
+    if not picked:
+        sys.exit(f"no notebook matches {sys.argv[1]!r}")
+    EXPORTS.mkdir(exist_ok=True)
+    for nb in picked:
+        for fmt in ("html", "markdown"):
+            subprocess.run(
+                [sys.executable, "-m", "nbconvert", "--execute",
+                 "--to", fmt, "--output-dir", str(EXPORTS), str(nb)],
+                check=True, cwd=ROOT,
+            )
+    for p in sorted(EXPORTS.iterdir()):
+        if p.suffix in (".html", ".md"):
+            print(f"wrote {p.relative_to(ROOT)} ({p.stat().st_size / 1024:,.0f} KB)")
+
+
+if __name__ == "__main__":
+    main()