docs(arr): chain completion — roots live on sonarr/radarr, PUID=0 identity fix rationale

Sonarr/Radarr root folders created via API (201). Lidarr/Readarr deferred to
first-run wizard (v1 validators demand quality-profile ids that don't exist
yet). Root cause of the write failures: LSIO PUID=1000 under rootless podman
maps to host uid 101000 — a phantom user owning nothing; PUID=0 maps to the
host user that owns every media dir.

serverAppConfigs-docs/Dankserver/ARR-Stack.md

@@ -364,6 +364,16 @@ per-arr qBittorrent clients (category = app name) → import**.
   and hand off to their own qB download client (category routing). Mappings
   materialize at grab time — zero mappings right after wiring is expected,
   not a fault.
+**Chain completion (same day):** Sonarr and Radarr root folders created via
+API (`/tv`, `/movies` → 201). Lidarr/Readarr roots deferred to their first-run
+wizard (v1 API validators demand quality-profile ids that don't exist yet — two
+clicks in the UI, not an API guess). The blocker under all of it: LSIO images
+run as `PUID=1000`, which under rootless podman's userns maps to host uid
+**101000 — a phantom user owning nothing**; Sonarr's own validator refused
+`/tv` with "not writable by user 'abc'" (placeholder name for the unknown
+uid). Fix: `PUID=0/PGID=0` on the arr stack + qbittorrent + prowlarr
+(container-root = host's `dank`, which owns every media dir; mapping-
+independent by construction). calibre-web and jellyfin untouched — not broken.
 
 ## Disk Layout