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/pyproject.toml

@@ -0,0 +1,36 @@
+[build-system]
+requires = ["setuptools>=68"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "teicalc"
+version = "0.1.0"
+description = "Genesys CX Cloud TEI (Forrester, Dec 2025) — composite reproduction + client overlay incl. the AI-token line"
+requires-python = ">=3.10"
+# The notebook is the deliverable (served with Mercury, exported via
+# nbconvert, tables via tabulate) — the whole toolchain is a required
+# runtime dependency, not an extra. `pip install -e .` must be enough.
+dependencies = [
+    "pandas>=2.0",
+    "plotly>=5.18",
+    "openpyxl>=3.1",
+    "mercury>=3.2",
+    "jupyterlab>=4.0",
+    "ipywidgets>=8.0",
+    "nbconvert>=7",
+    "tabulate>=0.9",
+]
+
+[project.optional-dependencies]
+dev = ["pytest>=7.4", "mypy>=1.8"]
+
+[tool.setuptools.packages.find]
+include = ["teicalc*"]
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]
+addopts = "-q"
+
+[tool.mypy]
+strict = true
+packages = ["teicalc"]