Add a `compat` job that type-checks the whole suite and a consumer fixture
against the minimum supported TypeScript (5.9), reusing the `dist/` artifact
`build` produced and gating `publish`. The compiler is resolved by npx, so it
never enters `devDependencies` or the local `check`/`verify` loop.
The fixture imports the package by name, resolving the emitted declarations
through the `exports` map; `expectTypeOf` / `.not.toBeAny()` make it reject an
`any`-typed declaration, which a bare compile would accept.
Correct the README consumer floor from >= 5.0 to >= 5.9 (set by `type-fest`)
and drop the `node10` resolution claim, which the exports-only entry never
satisfied.
tmu
75807c4bd8