feat(detector): implement Nodenv detection

[dipto0321]

Changes

• internal/detector/nodenv.go (full implementation):

  • Detect(): platform.LookupManagerBinary("nodenv") != "" OR $NODENV_ROOT env OR ~/.nodenv on disk (ASDF pattern)
  • Version(): nodenv --version, strips literal "nodenv " prefix, first whitespace-separated token, optional v prefix stripped
  • ListInstalled(): nodenv versions, lines * <v> / <v>, the trailing (set by <origin>) on current-version lines is stripped before semver parse; system sentinel filtered out
  • nodenvRoot() helper: $NODENV_ROOT → ~/.nodenv, mirrors asdfDataDir
  • Mutation methods return ErrNodenvNotImplemented sentinel (ASDF pattern)

• internal/detector/nodenv_test.go (24 mocked tests):

  • parseNodenvVersion: standard, git-revision suffix (1.6.2-12-gabc1234), v-prefixed, whitespace, empty, whitespace-only, no-version-after-prefix
  • parseNodenvInstalled: real output (with (set by ...) suffix), filters system sentinel, unsorted → sorted ascending, empty stdout, only blank lines, skips unparseable lines
  • Method tests: Name, Version (success capturing command, v-prefixed, runShell error, parsing error), ListInstalled (success, empty stdout, runShell error)
  • Detect: PATH-without-binary, dir-on-disk, $NODENV_ROOT override, empty env falls through, binary-on-PATH Windows-safe via nodenv.exe
  • MutationMethods_NotImplemented sentinel test
  • nodenvRoot helper: env-precedence, home-fallback, empty-when-no-home, whitespace-only-env-falls-through

Design notes

• The * <v> (current) line in nodenv versions carries a trailing (set by <origin>) annotation that asdf's output does NOT have. The parser strips everything from the first whitespace after the digits before handing to semver.NewVersion — this is the only behavioral divergence from parseASDFInstalled.
• The system sentinel is filtered explicitly (the system line is emitted iff nodenv-which node succeeds, i.e., there is a node on the system PATH outside Nodenv's managed versions — not a managed install).
• nodenvRoot() mirrors asdfDataDir() (same env → home fallback, same whitespace handling) for consistency.
• We use strings.CutPrefix("nodenv ") in parseNodenvVersion so unexpected branding like "Nodenv v1.6.2" errors loudly rather than silently returning the wrong token.
• Nodenv is documented as Unix-only — same posture as N; Windows users must use WSL or fall back to NVMWindows.

[cocogitto-bot]

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