docs: fix cleanup-related inaccuracies in CHANGELOG, managers.md, README

[dipto0321]

Summary

Three docs-only inaccuracies introduced alongside the post-upgrade cleanup
feature (PR #56 / issue #41), all surfaced by issue #60:

1. CHANGELOG.md cited the wrong issue for the native-mutation-commands
   bullet. It said "Closes chore(ci): gitignore the local bin/ and coverage.out #40", but chore(ci): gitignore the local bin/ and coverage.out #40 is chore(ci): gitignore the local bin/ and coverage.out — completely unrelated. The preceding
   bullet already closes feat(cleanup): post-upgrade cleanup prompt with version-by-version confirmation #41, so the redundant citation is just dropped
   (rather than double-citing feat(cleanup): post-upgrade cleanup prompt with version-by-version confirmation #41).

2. docs/managers.md described a fabricated nvm-windows suppression
   note. The paragraph claimed the cleanup prompt is suppressed for
   nvm-windows with a specific explanatory message. No such message
   exists in internal/cli/cleanup.go or internal/cli/upgrade.go. In
   reality, the cleanup prompt still runs against nvm-windows — each
   Uninstall() returns ErrNVMWindowsNotImplemented and surfaces that
   via the generic per-candidate "Failed to delete %s: %v" line. The
   Current() call also returns the sentinel, which triggers the
   ForcePerVersion downgrade (bug(cli): Current() failure leaves the active Node version unprotected from cleanup deletion #58), so even --cleanup / --yes /
   cleanup.auto: true fall back to y/N per candidate. The corresponding
   table row also said "prints a clear note" — corrected to describe the
   actual behavior.

3. docs/managers.md's "Manager not on PATH" failure mode was wrong.
   It said "the cleanup step is skipped entirely; the upgrade itself
   still completes." In reality, detector.ResolveManager returns
   ErrNoManager, and runUpgrade returns immediately at
   internal/cli/upgrade.go:111-114 — the entire upgrade aborts before
   install/migrate/cleanup. Rewritten to match.

4. README.md and docs/managers.md disagreed about Phase 7. README
   said "Phase 7 ✅" (done); managers.md said "Phase 7 in progress."
   Reconciled by flipping README to "Phase 7 🔧 (in progress)" with a
   pointer at the remaining distribution packaging work (chore(release): finalize GoReleaser config and npm wrapper #17 / chore(release): prepare v1.0.0 release #18),
   and clarifying managers.md's banner so the two are aligned on the
   same definition (cleanup + mutation shipped, distribution outstanding).

Linked issues

Closes #60

Type of change

• docs — documentation only
• feat — new feature (MINOR bump)
• fix — bug fix (PATCH bump)
• refactor — no behavior change
• perf — performance improvement
• test — tests only
• chore — maintenance / dependency bump
• ci — CI/CD only
• build — build system only
• Breaking change (MAJOR bump) — explain below

Checklist

• Title follows Conventional Commits (docs(scope): subject)
• I ran make ci locally and it passes (the change is docs-only; the
  Go pipeline still runs and stays green)
• I added or updated tests for the change (no test added — the "test"
  for a doc accuracy fix is git grep against the affected code paths,
  which is what verified the new wording matches reality)
• I updated relevant docs (this PR is the doc update; CHANGELOG.md
  gets a ### Fixed entry under [Unreleased])
• No new linter warnings (make lint green)
• If breaking: I documented the migration path in the PR body and
  updated CHANGELOG.md

Screenshots / output

Pre-fix, the CHANGELOG cited an unrelated CI/gitignore issue:

- Per-manager cleanup behavior is documented in
  `docs/managers.md#post-upgrade-cleanup`. Closes #40.

Post-fix (citation dropped; the adjacent bullet already closes #41):

- Per-manager cleanup behavior is documented in
  `docs/managers.md#post-upgrade-cleanup`.

Pre-fix, docs/managers.md claimed a fabricated single-note UX:

For nvm-windows, the upgrade proceeds normally but the cleanup
prompt is suppressed with a note: "nvm-windows cleanup is not yet
implemented — leave the old versions in place or remove them
manually via nvm uninstall <v> from an elevated shell."

Post-fix (describes the real per-candidate failure behavior):

For nvm-windows, the cleanup prompt still runs — it just
operates against a manager whose Uninstall() returns
ErrNVMWindowsNotImplemented for every candidate. Each
per-version Uninstall() call surfaces that sentinel via the
generic "Failed to delete %s: %v" line, so the user sees one
failure per version and can remove them manually via nvm uninstall <v> from an elevated shell. Because Current() also
returns the sentinel, the ForcePerVersion downgrade (see #58)
kicks in — even --cleanup / --yes / cleanup.auto: true will
prompt y/N for each candidate instead of mass-deleting.

Pre-fix, the "Manager not on PATH" failure mode was actively wrong:

Manager not on PATH — the cleanup step is skipped entirely;
the upgrade itself still completes (Install/SetDefault will
have already failed loudly if the manager wasn't there).

Post-fix (matches internal/cli/upgrade.go:111-114):

Manager not on PATH — detector.ResolveManager returns
ErrNoManager, and the entire upgrade command aborts before
reaching install/migrate/cleanup. There's no "cleanup-only
skipped" path; if the upgrade returns, the cleanup either
ran or was opted out of via --no-cleanup.

Pre-fix, README and managers.md disagreed on Phase 7's status
(README said done, managers.md said in progress); both now
reflect the same definition — cleanup + mutation shipped,
distribution packaging (#17 / #18) outstanding.

Files touched

• CHANGELOG.md — drops the wrong Closes #40 citation; adds a
  ### Fixed entry under [Unreleased] documenting the doc
  refresh with docs: post-upgrade cleanup docs inaccuracies (wrong issue ref, fabricated nvm-windows note, false PATH failure mode, Phase 7 status conflict) #60 reference.
• docs/managers.md — replaces the fabricated nvm-windows
  suppression-note paragraph with the real per-candidate failure
  behavior; corrects the "Manager not on PATH" failure-mode
  description; reconciles the Phase 7 status banner with README;
  updates the nvm-windows table row to describe the actual
  ErrNVMWindowsNotImplemented behavior instead of "prints a
  clear note."
• README.md — flips the Phase 7 row from "✅" to "🔧 (in
  progress)" with a pointer at the remaining distribution work
  so the two docs agree.

[cocogitto-bot]

✔️ dcebccc - Conventional commits check succeeded.