feat(install): seed deno.lock from package-lock.json
When `deno install` runs in a project that has a `package-lock.json`
but no `deno.lock`, translate the npm lockfile into deno.lock v5 format
and use it to seed resolution. Only applies to the local install
subcommand; other commands keep the previous behavior of starting from
an empty lockfile.
The translator handles scoped packages, nested node_modules resolution,
optional/peer dependencies, and OS/CPU constraints. Workspace links,
file/git/http deps, and packages without integrity are skipped.
