fix(install.sh): script-scope tmpdir so the EXIT trap doesn't trip set -u

[manzil-infinity180]

What

The installer aborts with bash: tmpdir: unbound variable (exit 1) after a successful install:

cilock v2.0.0-rc7 installed.
  $ cilock version
  ...
bash: line 161: tmpdir: unbound variable

Root cause

install.sh runs under set -euo pipefail. tmpdir was declared local inside main(), but the cleanup trap … EXIT fires in the global scope after main returns — where that local no longer exists. With -u (nounset), expanding the now-unset $tmpdir aborts the script.

Two consequences: the temp dir is never cleaned up (the rm never runs on the real path), and curl … | bash exits non-zero even though the binary installed fine — breaking any caller that checks the exit code.

Fix

Declare tmpdir at script scope (not local) and register a cleanup() EXIT trap once at the top, so the trap can see the real path and remove it. ${tmpdir:-} guards early exits.

+tmpdir=""
+cleanup() { [ -n "${tmpdir:-}" ] && rm -rf "$tmpdir"; }
+trap cleanup EXIT
 ...
-  local tmpdir
   tmpdir="$(mktemp -d)"
-  trap 'rm -rf "$tmpdir"' EXIT

Verification

Minimal repro of the two patterns under set -u:

• before: prints success, then tmpdir: unbound variable, exit 1 (matches the report).
• after: exit 0, temp dir cleaned up.

bash -n passes.