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/config.toml

@@ -0,0 +1,81 @@
+# Mercury app-shell theme — NTT DATA brand (light), modern surfaces.
+# See docs/brand.md for the source palette.
+#
+# Loaded from the directory where you launch `mercury` (this project root);
+# restart the server to apply changes. Only keys in mercury/config.py
+# CSS_VARIABLE_MAP emit a CSS variable — anything else in DEFAULT_THEME is
+# either derived or component-baked (e.g. success/warning/danger, slider
+# track, widget bg) and silently no-ops here. Omitted keys are derived
+# from the ones below.
+
+[main]
+title = "Genesys CX Cloud TEI — Business Case"
+favicon_emoji = "📊"
+footer = "Genesys CX Cloud TEI study (Forrester, Dec 2025)"
+notebooks_button_label = "Analyses"
+
+[welcome]
+header = "Genesys CX Cloud TEI"
+message = """
+Interactive reproduction of Forrester's *Total Economic Impact™ Of CX
+Cloud* composite ($10.8M NPV · 266% ROI). The published study is the
+verbatim anchor — including the AI-token line it models at $0; tune the
+🟡 client drivers live (and price the tokens), then export the
+personalized report source with `python scripts/export_report.py`.
+"""
+
+[theme]
+# ── Type — Georgia headings, Arial body. Both web-safe system fonts,
+#    so no font_url / network fetch. Georgia ships only normal+bold, so
+#    heading weight is 700 (the default 800 would render as faux-bold). ──
+font_family         = "Arial, 'Helvetica Neue', Helvetica, sans-serif"
+heading_font_family = "Georgia, 'Times New Roman', Times, serif"
+font_size           = "15px"
+font_weight         = "normal"
+heading_font_weight = "700"
+
+# ── Text — NTT ink scale ──
+text_color       = "#2e404d"   # body
+muted_text_color = "#586671"   # captions / secondary
+
+# ── Surfaces — white content floating on a soft neutral canvas (depth).
+#    For a strictly-white page instead, set background_color = "#ffffff". ──
+background_color         = "#f4f5f6"   # outer page
+content_background_color = "#ffffff"   # notebook column
+surface_color            = "#ffffff"
+card_background_color    = "#f8f8f8"   # brand card
+border_color             = "#d5d9db"   # brand border
+border_radius            = "10px"      # modern rounding
+
+# ── Accents — Future Blue. primary_color also drives the Run button + focus. ──
+primary_color             = "#0072bc"
+accent_color              = "#0072bc"
+focus_border_color        = "#0072bc"
+hover_background_color     = "#eef5fb"  # light blue tint
+selected_background_color = "#dcecfa"
+
+# ── Sidebar — clean white, hairline divider ──
+sidebar_background_color = "#ffffff"
+sidebar_text_color       = "#2e404d"
+sidebar_title_color      = "#151d2c"
+sidebar_shadow           = "1px 0 0 #d5d9db"
+
+# ── Top bar — deep NTT navy (brand heading-primary) ──
+topbar_background_color = "#151d2c"
+topbar_text_color       = "#ffffff"
+topbar_border_color     = "rgba(255,255,255,0.08)"
+
+# ── Footer ──
+footer_background_color = "#ffffff"
+footer_text_color       = "#586671"
+footer_border_color     = "#d5d9db"
+
+# ── Run button — subtle brand-blue gradient (else derives from primary) ──
+run_button_background       = "linear-gradient(180deg, #0087dc 0%, #0072bc 100%)"
+run_button_background_hover = "linear-gradient(180deg, #1a93e6 0%, #0079c8 100%)"
+run_button_text_color       = "#ffffff"
+
+# ── Depth — soft, navy-tinted shadows (modern) ──
+shadow_sm = "0 1px 2px rgba(21,29,44,0.05)"
+shadow_md = "0 6px 18px rgba(21,29,44,0.08)"
+shadow_lg = "0 16px 40px rgba(21,29,44,0.10)"