[dipto0321]

Closes #123

Summary

Adds Vite+ (vp, https://viteplus.dev) — VoidZero's unified toolchain — as a
ninth supported Node.js version manager. nodeup upgrade previously reported
"no Node.js version manager detected" for Vite+ users.

vp env exposes exactly the operations nodeup needs from a version manager,
so the new VitePlus manager drives it directly:

Operation	Command
Detect	vp on PATH, or <data>/bin/vp on disk (no subprocess)
Version	vp --version
ListInstalled	vp env list node --json
Current	vp env current node --json
Install / Uninstall / Use / SetDefault	vp env {install,uninstall,use,default} node@<v>
GlobalNpmPrefix	<data>/js_runtime/node/<v>/lib/node_modules

Data-directory resolution mirrors upstream's chain
(crates/vp_shared/src/dirs/resolution.rs): VP_HOME → <home>/.vite-plus
(only when it holds a current link) → VP_DATA_DIR → XDG / platform default.
All candidates are returned, not just the first hit, so nodeup can still find
Node installs when the shell it runs in doesn't carry the same Vite+ env vars
that vp itself would resolve.

One subtlety worth reviewing: Vite+ can run in system_first mode, where
the shims prefer the system Node over a managed runtime. In that mode
vp env current reports the system version — so Current() returns an error
instead of that version. nodeup treats a failed Current() as "active version
unknown" and fails closed on cleanup (issue #58) rather than attributing a
system install to the Vite+-managed set.

Also registered in the detector registry (unix + windows), taught the
system-node classifier that <data>/js_runtime/node is manager-managed (so a
vp-managed node on PATH no longer trips the "unrecognized layout" warning),
and refreshed the CLI prose and docs.

Verification

• make ci green (tidy + fmt + vet + lint + race tests)
• End-to-end against the real vp v1.4.0 on this machine:
  • nodeup list --manager vite-plus → vite-plus: 26.13.0
  • nodeup check → reports the system node as managed by vite-plus
  • nodeup upgrade --dry-run --manager vite-plus → resolves the manager and
    computes the plan
• Mutations (set default / use / install / uninstall) exercised against
  a throwaway VP_HOME=$(mktemp -d) sandbox, so the real Vite+ install was
  never mutated

Test plan

• go test ./internal/detector/... — new viteplus_test.go covers the
  three parse helpers, method argv assertions, error propagation
  (errors.Is), Detect() not shelling out, data-dir resolution, and
  GlobalNpmPrefix
• system_node_test.go — vite-plus cases added to the
  TestManagerManagedRoots table
• CI green on ubuntu / macos / windows

🤖 Generated with puku-cli

[cocogitto-bot]

✔️ e4455c9...bc93511 - Conventional commits check succeeded.