docs(spec,lint): record the intentional code divergence between the two name-like sets (#6734)

Two sets answer "is this field name record-title-ish", and they differ by
exactly one entry, `code`:

  packages/lint/src/data-model-rules.ts   NAME_LIKE_FIELDS  — has 'code'
  packages/spec/src/data/display-name.ts  NAME_ISH_EXACT    — does not

Per the maintainer's 2026-08-10 ruling on #6734 ("document the gap, no
behavior change"), both sets stay exactly as they are. What was defective
was that the divergence was invisible, not that it exists — so it is now
written down where both sets are defined, each pointing at the other:

- lint R9 (`object/missing-name-field`) asks the looser "will records be
  anonymous?" question — any readable face counts, so `code` counts;
- ADR-0079 derivation (`resolveDisplayField`) asks "what IS the title?" —
  an identifier is not a title, so `code` is deliberately absent from
  tier 1/2 and a `code`-only object derives at tier 3 instead.

`skills/objectstack-data/SKILL.md` taught the lint spelling as the
contract, so the drift was being taught; it gains the same distinction
note.

Nothing user-visible turns on the gap (R9 is `severity: 'suggestion'` and
the `Record #<id>` floor guarantees a title regardless).

ZERO behavior change: the diff is comments and prose only — no code path,
no test file, no generated output moves.

`docs/adr/**` is deliberately untouched: ADR-0079 records this as its open
question 4, and closing that ledger entry is a maintainer-merged ADR edit.

Closes #6734

Author: claude

packages/lint/src/data-model-rules.ts

@@ -33,6 +33,32 @@ const NUMERIC_TYPES = new Set([
   'number', 'currency', 'integer', 'decimal', 'percent', 'float', 'double',
 ]);
 const OPTION_FIELD_TYPES = new Set(['select', 'multiselect', 'radio', 'enum']);
+/**
+ * Field names that give an object a title FACE, for R9
+ * (`object/missing-name-field`).
+ *
+ * DIVERGES from spec's `NAME_ISH_EXACT`
+ * (`packages/spec/src/data/display-name.ts`) by exactly one entry: `code`. That
+ * difference is INTENTIONAL — the maintainer ruled on 2026-08-10 (#6734) to
+ * keep both sets as they are and write the gap down in both places rather than
+ * converge them. The two sets answer different questions:
+ *
+ *   - R9 asks the LOOSER **"will records be anonymous?"** — is there anything
+ *     here a human could read instead of a raw id? A `code` clears that bar, so
+ *     it counts as a title face and is listed below.
+ *   - ADR-0079 derivation (`resolveDisplayField`) asks **"what IS the title?"**
+ *     — which field to PICK as the primary. A `code` is an identifier, not a
+ *     title, so spec deliberately omits it from tier 1 (name-ish exact) and
+ *     tier 2 (name-ish affix). A `code`-only object can still be derived at
+ *     tier 3 ("first title-eligible field by declaration order") — by a
+ *     different rule and a different priority, so the two are not equivalent
+ *     even where they agree on the outcome.
+ *
+ * Nothing user-visible turns on the gap: R9 is `severity: 'suggestion'` and
+ * ADR-0079's `Record #<id>` floor means no object ships without a title either
+ * way. Do not "fix" either set into the other without a ruling that supersedes
+ * the one above.
+ */
 const NAME_LIKE_FIELDS = ['name', 'title', 'subject', 'label', 'full_name', 'display_name', 'code'];
 
 /** Child object names that read as line-items / composition (entered with the parent). */

packages/spec/src/data/display-name.ts

@@ -130,7 +130,30 @@ export function isTitleEligible(fieldDef: TitleEligibleFieldDef | undefined | nu
   return TITLE_ELIGIBLE_TYPES.has(type);
 }
 
-/** Exact name-ish field names (case-insensitive), highest derivation priority. */
+/**
+ * Exact name-ish field names (case-insensitive), highest derivation priority.
+ *
+ * DIVERGES from lint's `NAME_LIKE_FIELDS`
+ * (`packages/lint/src/data-model-rules.ts`) by exactly one entry: `code`. That
+ * difference is INTENTIONAL — the two sets answer different questions, and the
+ * maintainer ruled on 2026-08-10 (#6734) to keep both as they are and write the
+ * gap down in both places rather than converge them.
+ *
+ * This set answers **"what is the record's title?"** — it is tier 1 of
+ * {@link resolveDisplayField}'s derivation, i.e. the names whose presence is
+ * strong enough evidence to pick that field as the primary title outright. A
+ * `code` is an identifier, not a title, so it is deliberately absent here; a
+ * `code`-only object still gets a title, but at tier 3 ("first title-eligible
+ * field by declaration order") — by a different rule and a different priority.
+ *
+ * Lint R9 (`object/missing-name-field`) asks the looser **"will records be
+ * anonymous?"** question — does this object have any title FACE at all — and
+ * for that a `code` counts, which is why its set carries the extra entry. R9 is
+ * `severity: 'suggestion'` and the `Record #<id>` floor below guarantees a
+ * title regardless, so the two sets never disagree about an outcome a user
+ * sees. Do not "fix" either set into the other without a ruling that supersedes
+ * the one above.
+ */
 const NAME_ISH_EXACT: ReadonlySet<string> = new Set([
   'name', 'title', 'subject', 'label', 'full_name', 'display_name',
 ]);

skills/objectstack-data/SKILL.md

@@ -1103,6 +1103,20 @@ Data-model rules (in addition to naming/label/i18n):
 | `field/select-missing-options` | warning | a `select`/`multiselect`/`radio` with no `options` (or options source) |
 | `object/missing-name-field` | suggestion | an object with no `nameField` (ADR-0079's canonical title pointer) and no name-like field (`name`/`title`/`subject`/`label`/`full_name`/`display_name`/`code`) |
 
+> **`code` counts for R9, but is NOT a title-derivation key.** R9's name-like
+> list above is the *looser* of two "name-like" sets, and the difference is
+> deliberate. R9 asks **"will records be anonymous?"** — is there any readable
+> face at all — and a `code` clears that bar. ADR-0079's title derivation
+> (`resolveDisplayField`) asks the narrower **"what IS the title?"**, and its
+> name-ish set is `name`/`title`/`subject`/`label`/`full_name`/`display_name`
+> **without `code`** — an identifier is not a title. So an object whose only
+> name-ish field is `code` is R9-clean, yet its title is derived by the
+> lower-priority "first title-eligible field by declaration order" tier rather
+> than by name. Nothing user-visible turns on this (R9 is `suggestion`, and the
+> `Record #<id>` floor guarantees a title regardless), but do not read the R9
+> list as the derivation contract — set `nameField` explicitly when the title
+> matters.
+
 These same rules are the **rubric for AI-generated metadata** — a generation is
 "good" exactly when it is schema-valid and lint-clean: