✨ Add primitive union pattern matchers

Curried matchers over string|number literal unions in four variants
(exhaustive/partial x strict/widened return inference), per the header
matrix in src/primitive.ts.

- Adds type-fest for Simplify/ValueOf.
- Deliberate oxlint escape hatches (as any dispatch) until a cast-free
  formulation lands; see the file comments.

package.json

@@ -65,6 +65,9 @@
         "setup": "npm run setup:git-commit-message",
         "setup:git-commit-message": "git config commit.template commit-message-template"
     },
+    "dependencies": {
+        "type-fest": "^5.9.0"
+    },
     "devDependencies": {
         "@arethetypeswrong/cli": "^0.18.5",
         "@runwisp/pubv": "^1.5.1",