D296 — A KB's values converge on its own vocabulary

Decision. Lint knows families of status synonyms (lint.ValueSynonymFamilies) and a map may extend them with value_synonyms.<canonical>: [...]. The canonical member is always the KB's: the value its contract declares, or, when proposing a contract, the family's most frequent observed member. missing_value_contract on status carries a structured proposal (values plus a synonym and prose mapping). invalid_field_value carries set_value when the value is exactly one allowed value up to folding or by family. A new prose_value warning reports a sentence in a vocabulary field and carries split_value, which keeps the token in the field and moves the rest into the body. kb_repair applies both.

Why. D289 converged field names, but on five real KBs the larger rot was in values. A ~740-concept work KB had 16 distinct status values (done next to completato, in-progress next to in-corso, incidents resolved next to closed) and no contract, so concept_list(where: status=done) silently missed synonyms. Another KB used status as prose ("accepted — implemented in commit …"), so every such concept was a facet value of one. A third renamed stato → status (D289) and inherited Italian values as new synonyms. One KB had a deliberate backlog vocabulary (open, decision-needed, done) that a product-default normalisation would have destroyed.

On copies of those KBs the proposals came out as the KBs' own vocabularies with the synonyms mapped, and after declaring one ADR map's proposal with map_update, kb_repair prose_value converged its two prose statuses in one commit, prose kept in the body.

Alternatives rejected. A product vocabulary every KB is normalised to: it flattens KB-specific states. Per-concept fixes without a contract: deciding the vocabulary is a judgement, the same stance as D289. Dropping the prose: it is often the only record of a condition or a commit. An English-only family table: the drift measured was mostly in another language; extensible families with a declared contract escape hatch give an answer where one is known and none where it is not.

Consequences. ValueSynonymFamilies is documented row by row in docs/data-plane.md; a test fails if a value sits in two families or collides with a StandardFieldSynonyms key. lint.FixableChecks gains invalid_field_value and prose_value; kb_status.conformance counts both. Finding gains Proposal, returned as proposal. value_synonyms uses dotted keys like field_values.* (the frontmatter parser has no nested maps), not the nested form the plan sketched. A prose head of more than three words proposes its first word, so a value that starts with a long phrase may need an operator's correction of the proposal.