feat(harness): P3 per-run ABRA_DIR — structural recipe-tree isolation, recipe flock deleted

- run_recipe_ci.setup_run_abra_dir(): builds <runs_dir>/<run-id>/abra with servers/ and
  catalogue/ symlinked to the canonical ~/.abra (app .env files keep landing in the shared
  canonical path, so janitor discovery and env-based teardown are unchanged; per-domain
  filenames + the P2 app-domain lock prevent write conflicts) and a FRESH empty recipes/ —
  each run clones + checkouts its own recipe trees. Exported as $ABRA_DIR (honored by the
  abra CLI, verified on-host) before ANY abra call. Manual runs get manual-<pid> isolation.
- fetch_recipe(): plain clone into $ABRA_DIR/recipes/<recipe> — no shared-tree rm-rf, no lock.
  CCCI_SKIP_FETCH=1 now copies the canonically-staged clone into the per-run tree (same staging
  workflow, run reads staged state).
- abra.abra_dir()/recipe_dir(): single resolution rule ($ABRA_DIR else ~/.abra), used by
  recipe_checkout, has_lightweight_version_tags, recipe_head_commit, recipe_versions,
  generic._recipe_dir, lifecycle.prepull_images, snapshot_recipe_tests, and
  warm_reconcile._recipe_dir (which keeps the canonical default for its own systemd runs but
  follows the per-run tree when imported by promote_canonical inside a run).
- deleted: lifecycle.acquire_recipe_lock, RECIPE_LOCK_DIR, the main() call site and the
  must-lock-before-fetch ordering rule.
- tests/{ghost,discourse}/install_steps.sh: RECIPE_DIR resolves ${ABRA_DIR:-$HOME/.abra} so the
  compose.ccci.yml overlay lands in the tree the run actually deploys from (mechanical path fix
  required by per-run trees; no assertion/gate touched — see DECISIONS.md).
- .drone.yml comments updated (HOME=/root rationale now via the servers symlink).

runner/warm_reconcile.py

@@ -199,7 +199,13 @@ def _run(cmd, timeout=120, check=False):
 
 
 def _recipe_dir(recipe: str) -> str:
-    return os.path.expanduser(f"~/.abra/recipes/{recipe}")
+    # Resolve like the abra CLI does: $ABRA_DIR (the per-run tree when imported by a CI run,
+    # e.g. promote_canonical) else the canonical ~/.abra (this module's own systemd-timer runs,
+    # which set no ABRA_DIR). Keeps fetch_recipe (an `abra` subprocess) and the git readers
+    # below pointed at the SAME tree in both contexts.
+    return os.path.join(
+        os.environ.get("ABRA_DIR") or os.path.expanduser("~/.abra"), "recipes", recipe
+    )
 
 
 def recipe_tags(recipe: str) -> list[str]: