Docs: represent the DataJoint book's core principles (coverage review) #225

Umbrella tracking a book → docs coverage review: an audit of the core principles taught in the DataJoint book against the published documentation. Across ~37 principles in three clusters (integrity/keys, normalization, computation/reproducibility), the docs are solid overall — and stronger than the book on the make() reproducibility contract — with the gaps below.

New pages / major expansions

• Add an integrity-types explanation page (the seven integrity types) #217 — Integrity-types explanation page (the seven integrity types + rules→constraints map)
• Add a referential-integrity / foreign-keys explanation page #218 — Referential-integrity / foreign-keys explanation page (FK = runtime logical constraint, not a pointer; the five effects incl. auto-index)
• Expand normalization.md to the book's three-lens treatment #219 — Expand normalization.md to the three-lens treatment (+ the Order example that shows workflow normalization is stricter than 3NF)
• Add a Transactions / ACID explanation page #220 — Transactions / ACID explanation page

Targeted additions & one fix

• insert-data how-to: add insertion-discipline / reproducibility guardrails #221 — insert-data how-to: insertion-discipline / reproducibility guardrails (in progress)
• master-part spec: state that a dependency on the master implies its parts #222 — master-part spec: "a dependency on the master implies dependency on all its parts"
• Add an 'update data' how-to #223 — An "update data" how-to (updates are rare; delete + reinsert + recompute)
• Fix contradiction: autopopulate.md §5.5 shows a transaction inside make() #224 — Fix: autopopulate.md §5.5 shows a transaction inside make(), contradicting computation-model.md

Already addressed while this review ran

The audit baselined main, so these showed as gaps there but are closed on in-flight branches:

• "Referential integrity is impossible without entity integrity" → entity-integrity.md (docs: interlink schema-design concepts; fix PK/entity-integrity examples #216)
• Natural-key "real-world use" test in the how-to → design-primary-keys.md (docs: interlink schema-design concepts; fix PK/entity-integrity examples #216)
• Concept interlinking (normalization was a link-island; PK ↔ entity-integrity mutual) (docs: interlink schema-design concepts; fix PK/entity-integrity examples #216)
• Primary-key guideline corrections — dropped the fixed-width "joins faster" myth, "avoid dates", "avoid computed values"; added the floating-point-key warning (docs: interlink schema-design concepts; fix PK/entity-integrity examples #216)
• Delete → garbage-collection lifecycle link → delete-data.md

Where the docs already win (no action)

The make() reproducibility contract (formalized beyond the book), no-auto-increment rationale, the three questions of entity integrity, schema dimensions & lineage, cardinality-from-FK-placement, tripartite make(), and the mouse/cage normalization example.