fix(extract): don't flag the singular of a defined y→ies plural term

STRUCT-006's undefined-term scan skips a singular phrase whose plural is a
defined term, but the check only tried the bare "+s"/"+es" forms. For a term
whose final word takes a "y"→"ies" plural — "Licensed Facilities" defined,
"Licensed Facility" used — those forms produce "licensed facilitys" /
"licensed facilityes", so the singular was not recognized and leaked in as a
used-but-undefined term. (The regular "+s" case, "Licensed Products" →
"Licensed Product", already worked.)

Also test regularPlural(phrase), which produces the "ies" form; the bare
"+s"/"+es" forms are kept for a final word already ending in "s" ("Asset
Class" → "Asset Classes"), which regularPlural intentionally skips.

Zero golden churn: no fixture in the 327-doc corpus uses the singular of a
y→ies plural-defined term.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: clay-good

README.md

@@ -4,7 +4,7 @@
 
 **Vaulytica is the second pair of eyes you can cite.**
 
-`1,111 deterministic rules` · `20 cross-document checks` · `5 pre-disclosure checks` · `3 execution-readiness reconciliations` · `5 derived-deadline families` · `16 document sub-domains` · `88 state-law overlays (non-compete · security deposit · usury · will formalities)` · `10 export formats` · `0 servers` · `0 AI` · `5,860 passing tests` · `v9.41.0` · `MIT`
+`1,111 deterministic rules` · `20 cross-document checks` · `5 pre-disclosure checks` · `3 execution-readiness reconciliations` · `5 derived-deadline families` · `16 document sub-domains` · `88 state-law overlays (non-compete · security deposit · usury · will formalities)` · `10 export formats` · `0 servers` · `0 AI` · `5,861 passing tests` · `v9.41.0` · `MIT`
 
 ![Vaulytica landing page — "Drop legal docs. Get a report. Nothing leaves your browser."](docs/images/hero.png)
 
@@ -1332,7 +1332,7 @@ npm run dev          # open the printed URL
 npm run build        # static site → dist/
 npm run typecheck    # tsc --noEmit
 npm run lint         # eslint
-npm run test         # vitest — 5,860 tests, ~35s
+npm run test         # vitest — 5,861 tests, ~35s
 npm run coverage     # vitest + V8 coverage, enforces the regression floor
 npm run accuracy     # v5 Ground Truth harness → tools/accuracy/SCOREBOARD.md
 npm run mutation     # Stryker mutation score (scoped to extractors; slow, off the per-push path)

src/extract/definitions.test.ts

@@ -994,6 +994,21 @@ describe("plural compounds of defined terms", () => {
     );
     expect(map.undefined_capitalized.map((u) => u.term)).not.toContain("Licensed Products");
   });
+
+  it("does not flag the singular of a defined 'y'→'ies' plural term", () => {
+    // "Licensed Facility" is the singular of the defined "Licensed
+    // Facilities"; the bare "+s"/"+es" check produced "licensed facilitys"/
+    // "licensed facilityes" and missed it, leaking a STRUCT-006 false positive.
+    const map = extractDefinitions(
+      buildTree([
+        "Agreement",
+        '"Licensed Facilities" means the plants operated by Seller.',
+        "Each Licensed Facility shall be maintained.",
+        "A Licensed Facility may be inspected without notice.",
+      ]),
+    );
+    expect(map.undefined_capitalized.map((u) => u.term)).not.toContain("Licensed Facility");
+  });
 });
 
 describe("statute suffixes and office titles", () => {

src/extract/definitions.ts

@@ -709,8 +709,18 @@ export function extractDefinitions(tree: DocumentTree): DefinitionMap {
       // A SINGULAR use of a defined PLURAL term — "each Licensed Patent" where
       // "Licensed Patents" is the defined term — is that term's use, not a new
       // undefined one. (The mirror, a plural use of a defined singular, is
-      // handled by isCompoundOfDefined further down.)
-      if (definedNames.has(`${phraseLower}s`) || definedNames.has(`${phraseLower}es`)) continue;
+      // handled by isCompoundOfDefined further down.) The bare "+s"/"+es"
+      // forms are kept for a final word already ending in "s" ("Asset Class" →
+      // "Asset Classes"); regularPlural adds the "y" → "ies" case ("Licensed
+      // Facility" → "Licensed Facilities") that neither bare form produces.
+      const definedAsPlural = regularPlural(phraseLower);
+      if (
+        definedNames.has(`${phraseLower}s`) ||
+        definedNames.has(`${phraseLower}es`) ||
+        (definedAsPlural !== null && definedNames.has(definedAsPlural))
+      ) {
+        continue;
+      }
       // TITLE_CASE_PHRASE cannot cross an all-caps word, so a candidate is
       // often a truncation of a longer defined term — "Contractor Background"
       // cut from the defined "Contractor Background IP". A word-boundary