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.

assessments/CX_AI_Diagnostic/configs/financial_services.yaml

@@ -0,0 +1,14 @@
+# CX AI Advisory Diagnostic — financial-services overlay (STUB, MVP).
+#
+# The competency model and capping heuristic come from base.yaml unchanged.
+# Value drivers and unlock costs are not yet configured for this industry:
+# selecting it in the notebook scores capability normally but computes no
+# value-at-stake (an on-stage notice says so). Populate value_drivers and
+# unlock_costs before using this config with a client.
+
+extends: base
+industry: financial_services
+display_name: "Financial Services (stub)"
+
+value_drivers: []
+unlock_costs: {}