`cmd update` reports success but does not update the installed binary (when installed via bun)

Summary

cmd update prints "✔ Updated to v1.17.0" but cmd --version stays on the old version. No error is shown. The self-updater assumes npm
global install and never touches bun-installed binaries, so the update silently no-ops for bun users.

Expected Behavior

• cmd update upgrades the binary that is actually on PATH.
• After update, cmd --version shows the new version.
• If the binary did not change, the command reports failure (non-zero exit) with manual instructions — never a false success.
• --check-only behavior is preserved.

Actual Behavior

• cmd update always runs npm i -g command-code (hardcoded updateCommand in updateAction2 → runCliUpdateCommand).
• On a bun install (~/.bun/bin/cmd → bun global node_modules), the new version lands in npm's global dir as an orphan copy (no cmd bin link), while the PATH binary is untouched.
• Success is reported from the install command's exit code, not from the on-disk version changing.

Steps to reproduce the issue

1. Install via bun: bun i -g command-code
2. Run cmd update → prints "✔ Updated to v1.17.0. Run cmd to start using the new version."
3. Run cmd --version → still old version (e.g. 1.14.0)
4. Confirm orphan copy: ls /opt/homebrew/lib/node_modules/command-code (npm prefix) vs ls ~/.bun/install/global/node_modules/command-code (bun) — versions differ.

Command Code Version

1.14.0

Operating System

macOS

Terminal/IDE

ghostty

Shell

zsh

Session file (optional)

No response

Fix prompt (optional)

Fix the self-update logic so it updates the binary that is really on PATH:

1. Detect install method before updating. Inspect the resolved binary path (process.argv[1]; e.g. .bun/install/global/...,
   /opt/homebrew/bin, npx shim) and/or probe package-manager globals for command-code (bun: ~/.bun/install/global, npm: npm root -g,
   brew: brew list).
2. Update via the matching manager:
   • bun → bun i -g command-code@latest
   • npm → npm i -g command-code@latest
   • brew → brew upgrade command-code (if available)
   • unknown → current behavior + warning.
3. Verify after update. Compare the version of the resolved install before/after (package.json or --version). Report success only
   if the PATH binary version actually changed.
4. On stale binary → print failure with manual instructions, exit non-zero.
5. Keep --check-only semantics; keep telemetry, add install_method field if cheap.

Acceptance criteria:

• bun install: cmd update upgrades the bun copy; cmd --version shows new version; no orphan npm copy created.
• npm install: behavior unchanged.
• Update command succeeds but version unchanged → failure, non-zero exit, manual instructions.
• Unit tests cover: method detection (bun/npm/brew/path shims), command selection per method, post-update verification (success + stale
  cases).

Additional context

OS: macOS Tahoe 26.5.2

Traccia updateAction2 e runCliUpdateCommand, iniziando dall'updateCommand hardcoded e dal percorso risolto a partire da process.argv[1]. Usa i casi di unit test indicati per coprire bun, npm, brew e gli shim del percorso, quindi verifica che il binario risolto cambi dopo un aggiornamento e che gli aggiornamenti obsoleti falliscano senza modificare il comportamento di --check-only.