ensure the bun symlink on every run, not only after installing it

The link was made as part of install_bun, so a machine that already had bun never
got one. That is this machine: bun 1.3.14 in ~/.bun/bin, no /usr/local/bin/bun,
and `bun` resolving to nothing at all for root. Nothing has broken yet only
because `pm2 startup` has never been run here — the moment boot persistence is
enabled, all twenty ecosystem apps that say `script: 'bun'` fail at boot and work
perfectly when started by hand.

ensure_bun_symlink now runs whether or not this script did the install, and says
which of the three things happened: made it, found it already correct, or could
not find bun to link. The last records an error, since a missing link is a
reboot-shaped failure rather than a cosmetic one.

Safe across upgrades, which was the question: a symlink resolves by path, not by
inode, and `bun upgrade` replaces the file at $BUN_INSTALL/bin/bun rather than
moving it. Demonstrated by replacing a target with a new file — new inode, link
still resolves. It breaks only if the home directory goes, which breaks bun
anyway.

Also fixed the status line, which reported "not installed" on a machine with bun
in the user's home: it asked root's PATH, which is exactly what has no bun before
the link exists. bun_version now asks whichever copy is there.

This run created the link on this machine — /usr/local/bin/bun -> the account's
copy, and root can now run bun.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

scripts/setup/machine-setup/machine-setup.sh

@@ -1967,7 +1967,7 @@ if ! skip; then
   echo "     node   ${NODE_NOW:+v$NODE_NOW }${NODE_NOW:+-> }LTS $(node_lts_label)"
   echo "            pm2 is a Node application, and officer-pty compiles node-pty"
   echo "            against whatever Node is installed — there is no Linux prebuild."
-  echo "     bun    $(bun_installed && bun --version 2>/dev/null || echo 'not installed')"
+  echo "     bun    $(bun_installed && bun_version || echo 'not installed')"
   echo "            the platform itself, and nineteen of the twenty pm2 apps."
   echo "     pm2    $(pm2_installed && echo installed || echo 'not installed')"
   echo "            supervises all of them, and the ecosystem files are written for it."
@@ -1996,18 +1996,31 @@ if ! skip; then
 
   # ── bun ──
   if bun_installed; then
-    ok "bun $(bun --version 2>/dev/null) already installed"
+    ok "bun $(bun_version) already installed"
   else
     info "     installing bun..."
     if install_bun && bun_installed; then
-      ok "bun $(bun --version), symlinked to /usr/local/bin/bun"
-      SUMMARY+=("Bun: $(bun --version)")
+      ok "bun $(bun_version)"
+      SUMMARY+=("Bun: $(bun_version)")
     else
       warn "the bun install did not complete"
       ERRORS+=("Bun: install failed")
     fi
   fi
 
+  # Ensured every run, not only after an install. A machine that already had bun
+  # would otherwise never get the link, and the failure only shows up at the next
+  # reboot.
+  if ensure_bun_symlink; then
+    ok "bun symlinked to /usr/local/bin/bun — pm2 at boot has no ~/.bun on PATH"
+    SUMMARY+=("Bun: symlinked system-wide")
+  elif [[ -x /usr/local/bin/bun ]]; then
+    echo "     /usr/local/bin/bun already points at it"
+  else
+    warn "bun is not at ${USER_HOME}/.bun/bin/bun — cannot link it system-wide"
+    ERRORS+=("Bun: no system-wide symlink; pm2 apps will fail at boot")
+  fi
+
   # ── pm2 ──
   if pm2_installed; then
     ok "pm2 $(pm2 -v 2>/dev/null | tail -1) already installed"