Ingest structured data dictionary to enrich inferred schemas

[amc-corey-cox]

Implement a CLI option to accept a structured data dictionary file (format defined in #191) alongside data files, and merge the declared metadata into the inferred schema.

Behavior

• Run inference on data as usual (ranges, enums, optionality, etc.)
• Read the data dictionary and overlay its declarations onto the inferred schema
• Where they agree, use the richer information from the dictionary (e.g., add descriptions, units, coded value labels)
• Where they conflict, flag the discrepancy (see Reconciliation report: inferred schema vs. declared data dictionary #193)

Scope

• Extends the existing --data-dictionary-row-count concept but with a separate file and richer structure
• Pure data processing — no LLM dependency

Depends on #191. Part of #190.

[amc-corey-cox]

Downstream counterpart: linkml/dm-bip#307 (Enrich generated schemas with data dictionary metadata).