chore(build): remove outDir before tsup so no empty dirs survive

[lintdeveloper]

The one loose end from the #18 review. Build tooling only — no changeset, because consumers receive byte-identical output.

Problem

tsup's clean: true deletes files but leaves empty directories behind:

$ mkdir -p dist/data dist/nested/deep && pnpm build
empty dirs surviving tsup's clean:true:
    dist/data
    dist/nested/deep

That produced a phantom dist/data during the pre-publish integrity check on #18, making a docs-only release look like it had changed dist — the worst possible false alarm while deciding whether patch was the correct bump.

Fix

Remove the outDir outright before tsup. Deterministic, no new dependency:

"build": "node -e \"require('fs').rmSync('dist',{recursive:true,force:true})\" && tsup"

Verified

Planted dist/data and dist/nested/deep, then rebuilt:

empty dirs after fixed build          0
output vs published 0.5.0 dist        byte-identical ✓
lint ✓   tsc ✓   333 tests ✓   publint + attw ✓
package.json still biome-clean        ✓  (ci:version depends on this)

That last check matters — the release workflow runs biome format --write package.json, so a script edit that left the file unformatted would show up as noise in the next Version Packages PR.