feat(enrichment): add enum/union exhaustiveness-drift analyzer

Detect switches that covered every old enum or union member but omit a variant newly added by the PR.

Fixes #2028

Author: bohdansolovie

.env.example

@@ -69,7 +69,7 @@ GITTENSORY_REVIEW_ENRICHMENT=false
 # blameLink,approvalIntegrity,ciCheckSignals,undocumentedExport,staleBranch,commitHygiene
 # pendingReviewRequests,testRatio,migrationSafety,looseRange,terminology,todoMarker,magicNumber
 # conflictMarker,debugLeftover,sizeSmell,floatingPromise,deepNesting,errorSwallow,unsafeAny,a11y
-# i18n,unusedExport,commitLint
+# i18n,unusedExport,exhaustiveness,commitLint
 #
 # Profile defaults:
 # fast: dependency,dependencyDiff,lockfileDrift,secret,license,installScript,heavyDependency
@@ -82,14 +82,14 @@ GITTENSORY_REVIEW_ENRICHMENT=false
 # churnHotspot,blameLink,approvalIntegrity,ciCheckSignals,undocumentedExport,staleBranch
 # commitHygiene,pendingReviewRequests,testRatio,migrationSafety,looseRange,terminology
 # todoMarker,magicNumber,conflictMarker,debugLeftover,sizeSmell,floatingPromise,deepNesting
-# errorSwallow,unsafeAny,a11y,i18n,unusedExport,commitLint
+# errorSwallow,unsafeAny,a11y,i18n,unusedExport,exhaustiveness,commitLint
 # deep: dependency,dependencyDiff,lockfileDrift,secret,license,installScript,heavyDependency
 # hardcodedUrl,actionPin,eol,redos,provenance,codeowners,secretLog,assetWeight,typosquat
 # commitSignature,iacMisconfig,nativeBuild,history,docCommentDrift,duplication,churnHotspot
 # blameLink,approvalIntegrity,ciCheckSignals,undocumentedExport,staleBranch,commitHygiene
 # pendingReviewRequests,testRatio,migrationSafety,looseRange,terminology,todoMarker,magicNumber
 # conflictMarker,debugLeftover,sizeSmell,floatingPromise,deepNesting,errorSwallow,unsafeAny,a11y
-# i18n,unusedExport,commitLint
+# i18n,unusedExport,exhaustiveness,commitLint
 # END GENERATED REES ANALYZERS
 
 # Submitter-reputation spend control (internal-only): downgrades new/burst/low-rep

apps/gittensory-ui/src/lib/rees-analyzers.ts

@@ -1142,6 +1142,32 @@ export const REES_ANALYZERS = [
         "Conservative: re-export lists and `export *` are ignored (same as undocumented-export). Skips symbols shorter than 3 chars. Checks same-file references in the headSha file before querying default-branch Code Search (where brand-new PR exports are usually absent). Fail-safe on search errors or incomplete results.",
     },
   },
+  {
+    name: "exhaustiveness",
+    title: "Enum/union exhaustiveness drift",
+    category: "quality",
+    cost: "github-light",
+    defaultEnabled: true,
+    profiles: ["balanced", "deep"],
+    requires: ["files", "github-token", "head-sha"],
+    limits: {
+      maxFiles: 10,
+      maxFetches: 10,
+      maxFindings: 25,
+    },
+    docs: {
+      summary:
+        "Flags when a PR adds a new enum member or string-literal union variant but an exhaustive switch still omits it.",
+      looksAt:
+        "Added enum/union members in changed TS/JS files, comparing pre-PR vs headSha member sets and scanning changed files for switches that covered all old members.",
+      reports:
+        "Type file, line, union/enum name, added member, and optional consumer file — never file contents.",
+      network:
+        "Bounded GitHub contents fetches at headSha for changed source files. Requires GitHub token forwarding for private repos.",
+      notes:
+        "Conservative: only explicit enum/union case labels; switches with a default branch are skipped. Fail-safe on fetch errors or ambiguous type parsing.",
+    },
+  },
   {
     name: "commitLint",
     title: "Conventional-commit subjects",

review-enrichment/analyzer-metadata.json

@@ -1293,6 +1293,34 @@
         "notes": "Conservative: re-export lists and `export *` are ignored (same as undocumented-export). Skips symbols shorter than 3 chars. Checks same-file references in the headSha file before querying default-branch Code Search (where brand-new PR exports are usually absent). Fail-safe on search errors or incomplete results."
       }
     },
+    {
+      "name": "exhaustiveness",
+      "title": "Enum/union exhaustiveness drift",
+      "category": "quality",
+      "cost": "github-light",
+      "defaultEnabled": true,
+      "profiles": [
+        "balanced",
+        "deep"
+      ],
+      "requires": [
+        "files",
+        "github-token",
+        "head-sha"
+      ],
+      "limits": {
+        "maxFiles": 10,
+        "maxFetches": 10,
+        "maxFindings": 25
+      },
+      "docs": {
+        "summary": "Flags when a PR adds a new enum member or string-literal union variant but an exhaustive switch still omits it.",
+        "looksAt": "Added enum/union members in changed TS/JS files, comparing pre-PR vs headSha member sets and scanning changed files for switches that covered all old members.",
+        "reports": "Type file, line, union/enum name, added member, and optional consumer file — never file contents.",
+        "network": "Bounded GitHub contents fetches at headSha for changed source files. Requires GitHub token forwarding for private repos.",
+        "notes": "Conservative: only explicit enum/union case labels; switches with a default branch are skipped. Fail-safe on fetch errors or ambiguous type parsing."
+      }
+    },
     {
       "name": "commitLint",
       "title": "Conventional-commit subjects",