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/diaglib/__init__.py

@@ -0,0 +1,62 @@
+"""diaglib — the CX AI Advisory Diagnostic engine (Mercury Notebook Pattern).
+
+All math and data contracts live here; the notebook only arranges and
+renders. See docs/build_spec_v1.md for the instrument's specification.
+"""
+
+from .config import configs_dir, list_industries, load_config
+from .export import (
+    CSV_COLUMNS,
+    engagement_json,
+    load_engagement,
+    scores_dataframe,
+    write_exports,
+)
+from .models import (
+    BASELINE_FIELDS,
+    CONFIDENCE_ICON,
+    Competency,
+    CompetencyScore,
+    DiagnosticConfig,
+    DriverValue,
+    Engagement,
+    OperationalBaseline,
+    Participant,
+    UnlockMove,
+    ValueAtStake,
+)
+from .scoring import (
+    build_engagement,
+    build_scores,
+    dimension_rollup,
+    evidence_coverage,
+    heatmap_grid,
+    make_engagement_id,
+    parse_participants,
+)
+from .staging import backstage, on_stage
+from .value_math import (
+    MONTHS_18,
+    binding_constraints,
+    driver_value,
+    html_money,
+    money,
+    unlock_sequence,
+    value_at_stake,
+    weakest_foundational_score,
+)
+from .visuals import heatmap_fig, split_fig, unlock_fig, value_bands_fig
+
+__all__ = [
+    "BASELINE_FIELDS", "CONFIDENCE_ICON", "CSV_COLUMNS", "MONTHS_18",
+    "Competency", "CompetencyScore", "DiagnosticConfig", "DriverValue",
+    "Engagement", "OperationalBaseline", "Participant", "UnlockMove",
+    "ValueAtStake", "backstage", "binding_constraints", "build_engagement",
+    "build_scores", "configs_dir", "dimension_rollup", "driver_value",
+    "engagement_json", "evidence_coverage", "heatmap_fig", "heatmap_grid",
+    "html_money", "list_industries", "load_config", "load_engagement",
+    "make_engagement_id", "money", "on_stage", "parse_participants",
+    "scores_dataframe", "split_fig", "unlock_fig", "unlock_sequence",
+    "value_at_stake", "value_bands_fig", "weakest_foundational_score",
+    "write_exports",
+]