Installer should record Homebrew opt/<formula>/bin/node instead of Cellar paths #457

Context

Tracks the installer-side half of #446 / #445.

Today the live installer resolves Node through process.execPath / realpath and writes a versioned Homebrew Cellar path (e.g. /opt/homebrew/Cellar/node/26.7.0/bin/node) into install.json. After brew upgrade removes that keg, launchers fail with exit 127.

#445 covers the TUI side (Cellar → opt/<formula>/bin/node migration on update, repair hint). Users who already cannot start mcode must re-run the installer; until the installer records the stable path, a reinstall still pins Cellar again and only heals on the next in-app update.

Required change (installer release process; outside this repo)

For Homebrew-managed Node only, record:

<brew-prefix>/opt/<formula>/bin/node

Prefer opt/<formula>/bin over <brew>/bin/node so PATH prefixes stay scoped to the Node formula.

Keep realpath / current behavior for version managers whose links are per-shell or per-directory (fnm, asdf, volta).

Acceptance

• Fresh Homebrew installs write an opt/... nodeExecutable (no /Cellar/ in the receipt).
• Re-running the installer after brew upgrade restores a working launcher without waiting for an in-app update.
• Non-Homebrew Node installs are unchanged.

Related

• User report: CLI fails to start after brew upgrade removes the pinned Homebrew Node keg #446
• TUI fix PR: fix(tui): keep npm-prefix updates on the Node pinned by the receipt #445