fix: replace mkdirp with node's recursive mkdirSync

[unional]

Closes the second, separate cause of fixture's red dependency PRs. (The first is #247 — @swc/core build approval, which blocks #235 at install. These are independent.)

Why #197 could not pass

mkdirp v3 removed the default export:

mkdirp v3 exports: manual, manualSync, mkdirp, mkdirpManual, mkdirpManualSync,
mkdirpNative, mkdirpNativeSync, mkdirpSync, native, nativeSync, sync,
useNative, useNativeSync

There is no default, so import mkdirp from 'mkdirp' has nothing to bind and the build fails. The renovate PR bumps the version without touching the two call sites, so it can never go green on its own.

Why drop it rather than migrate to mkdirpSync

mkdirp.sync has been a thin wrapper over fs.mkdirSync(path, { recursive: true }) since Node 10. ensureFolderExist() is the only caller in ts/, plus one in a spec. Removing the dependency:

• retires fix(deps): update dependency mkdirp to v3 - autoclosed #197 permanently instead of re-passing it,
• removes the stale @types/mkdirp (v1 types pinned against a v2 runtime),
• drops a runtime dependency from the published package.

Behaviour is identical.

Verification

pnpm verify with no mkdirp installed: 7 suites / 63 tests pass, coverage unchanged.

Patch changeset included, since this changes the published package's dependency list.

[changeset-bot]

🦋 Changeset detected

Latest commit: 4e085ac

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@unional/fixture	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.19%. Comparing base (c74c00d) to head (4e085ac).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #248   +/-   ##
=======================================
  Coverage   97.19%   97.19%           
=======================================
  Files           9        9           
  Lines         321      321           
  Branches       86       87    +1     
=======================================
  Hits          312      312           
  Misses          9        9           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.