setup_datadict(): generate a tidyverse data-dict.yaml from the dictionary and tidy data

[larnsce]

Motivation

tidyverse/data-dict is an emerging YAML specification (v0.1.0) for data dictionaries: semantic types (number(id), number(quantity) + units, enum + values), constraints (primary_key, foreign_key, required, assertions), cross-table relationships, and a domain glossary — all machine-readable and AI-agent-readable. Full analysis: dev/research-data-dict-integration.md.

data-raw/dictionary.csv is a flat, weaker version of one tables: block. This issue is the additive first step (Option A in the research doc): keep the CSV as the authoring surface and generate data-dict.yaml from it, the same way setup_roxygen() and generate_jsonld() are downstream renderings today.

Proposal

New exported function setup_datadict() (with an update_datadict() re-run path, consistent with the v1.1.0 idempotency sweep in #73) that writes data-dict.yaml at the package root:

• dataset-level name / description from DESCRIPTION (via desc)
• one tables: entry per .rda in data/
• column name and description from data-raw/dictionary.csv
• type mapped from R classes: character → string, numeric/integer → number, factor → enum + values from levels, logical → boolean, Date → date, POSIXct → datetime
• examples: (first ~5 distinct values) and range: (min/max for numeric/date) drawn from the data — cheap since collect_tidydata_info() already loads every dataset

YAML emission via yaml::write_yaml() (one small new dependency). No dependency on the Rust CLI — generation is pure R.

Acceptance criteria

• Running setup_datadict() on a package with a completed dictionary produces a data-dict.yaml that passes data-dict validate-spec
• Re-running preserves hand-added enrichments (units, constraints) or clearly documents the regeneration contract
• Behavioral test per the v1.2.0 test bar; documented in the vignette

Related: #13 (updating an existing dictionary), #83 (AI-assisted descriptions — data-dict ships agent skills for authoring dictionaries).