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_Discovery_Workshop/README.md

@@ -0,0 +1,116 @@
+# CX Exploration & Discovery Workshop
+
+An **Assessment** — a reusable workshop master (see
+[`docs/Assessment_Pattern_V1-00.md`](../../docs/Assessment_Pattern_V1-00.md))
+— and a **live facilitation aid** for a CX discovery session, built on the
+[Mercury Notebook Deliverable Pattern](../../docs/Mercury_Notebook_Pattern_V1-00.md).
+Unlike the TEI business-case studies, this deliverable computes no dollars —
+its "numbers" are **topic status and progress**. The Mercury stage is the
+visual you share on a call or in a workshop while you work through the
+questions; the question script and captured notes live backstage and export
+as LLM input for the survey write-up or a downstream business case.
+
+## What the client sees (the stage)
+
+A calm **topic board**: each topic, its one-line scope, a status glyph, and —
+for the topic under discussion — a **live sub-topic checklist**, above a
+**progress bar** ("3/8 topics complete"). No wall of questions: you ask those.
+
+![board preview](docs/board_preview.png)
+
+You drive it from the sidebar — a **status** selector and a **notes** box per
+topic, plus a **checkbox** per sub-topic. As the conversation moves you set a
+topic *In progress*, tick sub-topics as you cover them, mark it *Complete* (or
+*Skipped*), and jot answers. Every change re-renders the board and progress bar
+(Mercury re-runs the cells below the widgets).
+
+## What you work from (backstage)
+
+JupyterLab and the exports carry the **facilitator question script** (all 95
+prompts, grouped by topic → sub-topic) and the **captured-session appendix**
+(status + notes as a markdown table and one JSON block). Neither shows on the
+Mercury stage. The 8 topics / 26 sub-topics / ~110-minute agenda are the
+structured form of the source survey.
+
+## Where the content lives: in the notebook
+
+Two tagged cells of
+[`notebooks/cx_discovery.ipynb`](notebooks/cx_discovery.ipynb) carry
+everything a consultant edits — **in Jupyter, never in a `.py` file**:
+
+- **`topic-bank`** — the workshop content: every topic, sub-topic, and
+  facilitator prompt. It is the study's verbatim anchor: wording tracks the
+  source survey [`docs/cx_discovery_survey.md`](docs/cx_discovery_survey.md)
+  (the original `cxxm.md`), and the `key` slugs are stable identities the
+  sidebar widgets, captured notes, and JSON export all key off — never
+  renumber or rename them casually. The cell's own comment block carries the
+  full editing rules.
+- **`engagement-data`** — the client facts (client, workshop date,
+  facilitator, attendees). **Placeholders in this master**; filled in the
+  engagement copy. The values flow to the stage board header, the export
+  preamble, and the JSON appendix `meta`.
+
+`discoverylib/` holds **code only**: the `Topic`/`SubTopic` schema, the
+status vocabulary, and the session engine — every engine function takes the
+bank as its first argument. The ~42 sidebar widgets are built by a runtime
+loop over `TOPICS`, so board, checklist, script, gate, and export all pick up
+a content edit automatically. The test suite reads the tagged cells straight
+out of the notebook (no kernel) and pins content shape, so `pytest` guards
+the bank exactly as shipped.
+
+## Layout
+
+```
+notebooks/cx_discovery.ipynb   # THE deliverable — content + data + presentation
+                               #   tagged cells: topic-bank · engagement-data ·
+                               #   presentation ×4 · gate · data-appendix
+                               #   stage shows ONLY: title · progress line · board
+discoverylib/           # the engine — code only, no content
+  session.py            #   Topic/SubTopic schema, status vocabulary, progress, export payload
+  staging.py            #   stage/backstage detection (+ backstage_md for the appendix)
+scripts/export_report.py       # execute once → exports/*.html + LLM-ready *.md
+tests/                  # content + engagement pins (read from the notebook), engine pins, staging
+docs/cx_discovery_survey.md    # source survey (the original cxxm.md)
+exports/                # generated report sources (never committed)
+```
+
+## Run
+
+```bash
+python -m venv .venv && source .venv/bin/activate
+pip install -e ".[dev]"
+
+mercury --working-dir .                # serve the stage (share this screen)
+jupyter lab                            # analyst / facilitator view
+pytest                                 # content + engagement + engine + staging pins
+jupyter nbconvert --to notebook --execute --inplace notebooks/cx_discovery.ipynb   # gate
+python scripts/export_report.py        # exports/*.html + *.md for the LLM handoff
+```
+
+The `.md` export opens with a generated preamble (what the document is, the
+engagement line, how to read it) and ends with the **Session state (JSON)**
+block — the machine source of truth for the write-up. Presentation cells
+(setup, the facilitator run-book, widgets, board) are stripped from it; the
+HTML export keeps the full presentation for human review.
+
+## Extending
+
+New or reshaped discovery content is an edit to the notebook's `topic-bank`
+cell in JupyterLab, then:
+
+1. Re-run the notebook — the in-notebook **gate** recounts the bank
+   (topics / sub-topics / prompts / key order / agenda minutes); update its
+   pins if the change is deliberate.
+2. `pytest` — `tests/test_topics.py` pins the same shape from outside the
+   kernel; re-pin the counts there too.
+
+Add a topic and the sidebar controls, board, checklist, script, gate, and
+export all pick it up — they're all derived from `TOPICS` at runtime. New
+*logic* (not content) goes in `discoverylib/session.py` with pins in
+`tests/test_session.py`.
+
+**Running this for a client?** Don't fill client data into this master —
+follow the copy-out checklist in
+[`docs/Assessment_Pattern_V1-00.md`](../../docs/Assessment_Pattern_V1-00.md):
+copy the directory out of Palladium, stamp it `YYYYMM_Client_CX_Discovery`,
+fill the `engagement-data` cell there, and treat the copy as confidential.