docs: document NPM dedicated-port jail convention and zsh $path footgun

Two real gotchas from today's goddy->gringo Laravel migration: every jail
on an NPM-fronted host needs a dedicated listen port (8000+last-octet),
not just the shared port 80, or NPM cutover silently can't reach it even
though every direct/Host-header test passes. Separately, zsh ties a
variable literally named `path` to $PATH itself - overwriting it broke
every subsequent command in a config-editing script with no clear error.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

skills/remote-shell-quoting-safety/SKILL.md

@@ -60,6 +60,26 @@ decode step per real filesystem boundary crossed is enough.
   special characters — check for quoting corruption before looking
   elsewhere.
 
+## zsh footgun: never name a variable `path` (or a few other reserved names)
+
+If the remote host's shell is zsh (several boxes in this fleet default to
+it), assigning a plain string to a variable literally named `path` does
+not create a normal local variable — zsh ties the lowercase `path` array
+to `$PATH` (colon-joined ⇄ array elements) automatically. Overwriting it
+with a single string **replaces `$PATH` itself**, and every subsequent
+command in that shell (including ones on later lines of the same script)
+fails with `command not found: cp` / `command not found: awk` / etc. —
+confirmed live 2026-08-07 editing nginx configs over SSH into a zsh
+remote shell, where a loop using `path="/usr/local/etc/nginx/..."` broke
+every command after the assignment with no explanation beyond
+`command not found`. **Rename to anything else** (`cfgpath`, `target`,
+`dest`, ...) — this isn't specific to nginx configs, it'll happen with
+any script that happens to pick `path` as a variable name on a zsh
+remote. A few other zsh-reserved lowercase names exist for the same
+reason (`status`, `pipestatus`) — when in doubt, avoid single common
+English words as variable names in scripts meant to run under an
+unknown/remote shell, or check `typeset -p <name>` first if unsure.
+
 ## What NOT to do
 
 Don't respond to a quoting failure by adding more layers of escaping