Non-pnpm package managers

Support npm and yarn repos in the sandbox: their own shared dep-store wiring (npm cache / yarn cache), lockfile hashing (package-lock.json / yarn.lock) for the snapshot key, and correctness coverage for their install layouts.

Why deferred: The generic-any-repo goal implies it eventually, but every current consumer is pnpm: the dep store is pnpm-specific (.virrun/store/pnpm, pnpm env wiring), computeLockfileHash reads pnpm-lock.yaml, and the differential/equivalence corpora exercise pnpm installs. Each added manager multiplies the correctness matrix (managers × native deps × cache states × hosts) — a real ongoing gate surface with no consumer to pay for it. The sandbox itself is manager-agnostic (bwrap runs any process); only the cache/key plumbing is pnpm-shaped.

Revisit when: An external consumer repo on npm or yarn wants virrun — the store/lockfile seams get abstracted then, driven by a real install to gate against.

Cheaper interim: An npm/yarn repo can still run non-install commands sandboxed today; only the warm-snapshot install path and its keying assume pnpm.

Native task-cache recording

Let the native backend produce task-cache entries, so skip-unchanged-builds works without the os sandbox.

Prepare layer narrow key

Key the prepare layer on the inputs nuxt prepare actually reads instead of the whole source-tree hash.