feat: add master notebook library scaffolding and review tooling

Add CLAUDE.md defining the Palladium master notebook conventions and
Red Panda Approval criteria, plus a review-notebook slash command for
LLM-driven notebook review.

Expand .gitignore to block client/engagement documents and generated
exports, keeping masters client-clean while allowing text/image sources.

Normalize slider widget numeric values from floats to integers in
notebook JSON.

docs/Athena_TEI.md

@@ -690,3 +690,27 @@ All arithmetic uses Python `Decimal` to avoid floating-point drift. Values are s
 ---
 
 *TEI Tool — Athena*
+
+---
+
+## Palladium conventions (client-side)
+
+Relocated from the root README (2026-07); these are Palladium's bridges where the
+Forrester methodology and the Athena TEI API differ.
+
+### Methodology bridges (Palladium ↔ Athena)
+
+| Topic | Athena behaviour | Palladium convention |
+|---|---|---|
+| **Cost risk adjustment** | Costs are never risk-adjusted server-side | Cost values are pushed pre-multiplied by `(1 + risk_adj)`; field-level adjustment stays 0 |
+| **Year-0 "Initial" costs** | No year-0 concept; non-annual values are folded into Year 1 | Each cost gets a companion non-annual `<key>_initial` field. `TEIClient` folds them back into an `initial` key on read. Athena discounts these as Year 1 (Forrester doesn't discount Year 0) — expect ≈0.15% drift on cost PV |
+
+### Scenario analysis (`core.calculations.SCENARIOS`)
+
+Three scenarios model uncertainty in adoption and realization:
+
+| Scenario | Adoption | Risk delta | Effect |
+|----------|----------|------------|--------|
+| Conservative | 80% | +10pp on benefits | Lower benefits, higher modelled cost |
+| Moderate | 100% | 0 | Base case (= published study) |
+| Aggressive | 115% | –5pp on benefits | Higher benefits, lower padding on cost |