fix: audit MEDIUM fixes — merge fallback, service hardening, CI token

- moonarch-waybar: on merge failure, remove the stale output so waybar
  falls back to the system config (previously it kept running with stale
  merged data despite the error notification claiming otherwise).
- moonarch-doctor: hoist INSTALLED assignment above both OFFICIAL and AUR
  blocks so the script survives set -u when only aur.txt is present.
- zshrc parse_git_branch: gate on git rev-parse and replace three grep
  subshells with bash pattern matching, cutting prompt latency from
  ~5 subprocesses per render to 2 (status + symbolic-ref).
- moonarch-batsaver.service: validate the threshold is an integer 1-100
  before writing to sysfs, add NoNewPrivileges and protection directives
  instead of relying on kernel validation alone.
- ci/act-runner/Dockerfile: drop the broad "pacman -Sy *" sudoers entry
  (only -S --needed is required by makepkg), and pin run.sh to
  act_runner:0.3.1 so it cannot drift ahead of the pinned binary.
- .gitea/workflows/update-pkgver.yaml: push via credential.helper=store
  with a chmod 600 temp file instead of `git -c http.extraHeader=...`,
  so the token no longer shows up in /proc/PID/cmdline.

defaults/etc/systemd/system/moonarch-batsaver.service

@@ -9,7 +9,19 @@ ConditionPathExists=/var/lib/moonarch/batsaver-threshold
 
 [Service]
 Type=oneshot
-ExecStart=/bin/sh -c 'cat /var/lib/moonarch/batsaver-threshold > /sys/class/power_supply/BAT0/charge_control_end_threshold'
+# Validate the threshold (integer 1–100) before writing. The state file is
+# written by wheel-group users via moonarch-batsaver-toggle; the kernel rejects
+# non-numeric values on sysfs, but validating here prevents noise on boot and
+# makes the trust boundary explicit.
+ExecStart=/bin/sh -c 'V=$(cat /var/lib/moonarch/batsaver-threshold); case "$V" in ""|*[!0-9]*) exit 0;; esac; [ "$V" -ge 1 ] && [ "$V" -le 100 ] && printf %s "$V" > /sys/class/power_supply/BAT0/charge_control_end_threshold'
+NoNewPrivileges=true
+ProtectHome=true
+PrivateTmp=true
+ProtectKernelModules=true
+ProtectControlGroups=true
+RestrictNamespaces=true
+RestrictRealtime=true
+LockPersonality=true
 
 [Install]
 WantedBy=multi-user.target