fix: resolve 17 confirmed bash-parity drifts from port review

Adversarial parity review of every ported action against its bash source
confirmed 17 real behavioral drifts (of 22 claimed); all fixed here:

- tiers/chown: defaults were compositions/apex/tierN (one level too deep);
  now the tier roots. shared/ base reset is non-recursive again.
- compose: --dry-run was swallowed by argparse.REMAINDER; now stripped.
- host.write_file: rendered files land 0644 (tempfile's 0600 made fresh
  systemd units/crowdsec configs owner-only).
- systemd.deploy_units: top-level non-hidden files only.
- ufw: missing docker/host config dir exits 66; missing /etc/ufw target
  aborts; empty rules dir warns; dotfile .rules excluded.
- sync/packages: Telegram error-trap parity and failed notify exits 1.
  Same notify-failure exit for backup/run and sync/repository.
  repository regains the node-dir guard.
- tiers/useradd: no more secret-bearing .env.bak per run.
- tiers/link: EOF on confirm prompt declines and continues.
- extract-traefik-certs: sudo mkdir inside the notify envelope.
- generate-happ-subscriptions: realpath parent-exists guards + docker check.
- configure/crowdsec: bouncer install goes through install_packages.
- lint-docker-compose: malformed/unreadable anchor-IP inputs are lint errors.
- core compose: APEX_RESTIC_REPOSITORY now ?error; RESTIC_COMPRESSION
  per-node via APEX_RESTIC_COMPRESSION (default auto).
- sys.service_exists line-anchored; tpl docstring corrected.

actions/utils/generate-happ-subscriptions.py

@@ -1,6 +1,7 @@
 # actions/utils/generate-happ-subscriptions.py
 """Port of utils/generate-happ-subscriptions — build + run the happ generator image."""
 import os
+import shutil
 from engine.descriptor import Meta, Arg
 
 METADATA = Meta(summary="Generate .psub files from a JSON config via the happ generator (docker).",
@@ -11,6 +12,16 @@ def run(ctx, args):
     log = ctx.log
     src_dir = os.path.join(ctx.paths.commons, "source", "happ-subscription-generator")
     inp, out = os.path.realpath(args.input_json), os.path.realpath(args.output_dir)
+    # GNU realpath (bash) fails unless all but the last component exist — without this
+    # guard a mistyped path reaches `docker run -v`, which creates it root-owned.
+    for label, p in (("input_json", inp), ("output_dir", out)):
+        parent = os.path.dirname(p)
+        if not os.path.isdir(parent):
+            log.error(f"Cannot resolve {label}: no such directory: {parent}")
+            raise SystemExit(1)
+    if not shutil.which("docker"):
+        log.error("docker is not installed or not in PATH.")
+        raise SystemExit(1)
     log.info(f"Building {IMAGE}...")
     ctx.sys.run(["docker", "build", "-t", IMAGE, src_dir], check=True)
     log.info(f"Running generator: {inp} -> {out}")