fix: refresh npx cache for local bin changes

[cyphercodes]

Fixes #9766

Summary

• avoid reusing a stale npx cache entry when a local directory package changes its bin map
• include the current local directory bin map in the npx cache key
• add regression coverage for adding a new local bin between sequential npm exec runs

Testing

• npm --workspace=libnpmexec exec -- tap test/local.js --grep 'bin changes|same-named local bins' --no-coverage
• npm --workspace=libnpmexec exec -- eslint lib/index.js test/local.js
• git diff --check