✨ Compile doc code fences into tests

Every `ts`-tagged fence in README.md / CONTRIBUTING.md now becomes an
executed `node:test` case in a gitignored generated file, so a
documented example cannot drift from the API. The generator hoists and
merges the leading imports, rewrites the library specifier to the
`#test-tiny-pattern-ts` alias, and rejects a fence with no describing
paragraph or one that re-imports a prelude module.

CI regenerates via `pretest:ci`; `create:doc-tests` runs the generator,
formats, then typechecks the output against a scoped tsconfig that
relaxes `noUnusedLocals`. c8's default excludes already omit the
generated `*.test.ts`, so `test:ci` is unchanged.

README.md

@@ -63,6 +63,8 @@ Add a fallback as the second argument to leave members unhandled; the fallback
 receives the remainder:
 
 ```ts
+import { getPrimitiveUnionMatcher } from "tiny-pattern-ts";
+
 const matchLabel = getPrimitiveUnionMatcher<"yes" | "no" | "maybe">();
 
 const label = matchLabel(