update README media model — arr_sync.sh union replaces ownership split

Old model: HOST1 owns Movies/TV/Music, HOST2 owns Anime — each arr
manages different shares to prevent conflicts.

New model: arr_sync.sh syncs all arr databases bidirectionally before
every rsync cycle. Either server can download to any share at any time.
The databases converge (union, not overwrite), then rsync spreads files
additively. Neither server owns a share. The union is the source of truth.

Also updates share name annotations and removes the "read-only mirror"
framing from the share naming section.

README.md

@@ -131,11 +131,11 @@ as sync targets and mount points — a mismatch is a broken path.
 # the share on HOST2 must have the exact same name.
 #
 # Same name on both servers:
-    /mnt/user/Movies          # HOST1 source of truth, HOST2 mirror
+    /mnt/user/Movies          # both servers — arr_sync.sh keeps Radarr in union
-    /mnt/user/Tv_Shows        # HOST1 source of truth, HOST2 mirror
+    /mnt/user/Tv_Shows        # both servers — arr_sync.sh keeps Sonarr in union
-    /mnt/user/Music           # HOST1 source of truth, HOST2 mirror
+    /mnt/user/Music           # both servers — arr_sync.sh keeps Lidarr in union
-    /mnt/user/Anime_Shows     # HOST2 source of truth, HOST1 mirror
+    /mnt/user/Anime_Shows     # both servers — arr_sync.sh keeps Sonarr in union
-    /mnt/user/Anime_Movies    # HOST2 source of truth, HOST1 mirror
+    /mnt/user/Anime_Movies    # both servers — arr_sync.sh keeps Radarr in union
 #
 # rsync.sh syncs /mnt/user/Movies on HOST1 → /mnt/user/Movies on HOST2.
 # If HOST2 has it at /mnt/user/Movies-Mirror → rsync aborts: path not found.
@@ -168,46 +168,61 @@ across separate shares per-user or per-application.
 
 ---
 
-### ── Never Two Arrs Against the Same Share Simultaneously ───────────────────
+### ── Both Arrs Manage All Shares — arr_sync.sh Is the Source of Truth ───────
 
 ```bash
 # ─────────────────────────────────────────────────────────────────────────────
-# This rule is absolute. No exceptions.
+# Both servers run Sonarr, Radarr, and Lidarr — all pointing at the same
+# share names. Either server can download anything to any share at any time.
 #
-# Correct: HOST1 Sonarr manages /mnt/user/Tv_Shows
+# How it stays coherent:
-#          HOST2 Sonarr manages /mnt/user/Anime_Shows
+#   arr_sync.sh runs first (before rsync) — bidirectional library union.
-#          Different shares — no conflict
+#   Both Sonarr instances know about every TV episode on either server.
+#   Both Radarr instances know about every movie on either server.
+#   Both Lidarr instances know about every album on either server.
 #
-# Correct: HOST1 Tdarr transcodes from /mnt/user/Anime_Shows
+# Then rsync spreads the files additively (no --delete).
-#          HOST2 Sonarr downloads into /mnt/user/Anime_Shows
+# Any file downloaded on HOST1 propagates to HOST2 on the next cycle.
-#          But: they run in non-overlapping time windows
+# Any file downloaded on HOST2 propagates to HOST1 on the next cycle.
 #
-# WRONG:   HOST1 Sonarr AND HOST2 Sonarr both managing /mnt/user/Tv_Shows
+# HOST1 downloads Tv_Shows episode:
-#          Two arrs managing the same library = rename conflicts, double imports,
+#   → HOST1 Sonarr tracks it immediately
-#          deletion battles, corrupted databases.
+#   → arr_sync.sh runs → HOST2 Sonarr now tracks it
+#   → daily rsync → file lands on HOST2
 #
-# This is why source of truth is split:
+# HOST2 downloads the same show's next episode that same night:
-    HOST1 owns:  Movies (Radarr), Tv_Shows (Sonarr), Music (Lidarr)
+#   → HOST2 Sonarr tracks it immediately
-    HOST2 owns:  Anime_Movies (Radarr), Anime_Shows (Sonarr)
+#   → arr_sync.sh runs → HOST1 Sonarr now tracks it
+#   → daily rsync → file lands on HOST1
 #
-# When HOST2 enters failover and starts HOST1's arr containers — those arrs
+# Both servers converge. Neither owns the share. The union is the truth.
-# point at /mnt/user/Movies etc. HOST2's own arrs point at /mnt/user/Anime_*.
-# Different shares, no conflict. This is by design.
 # ─────────────────────────────────────────────────────────────────────────────
 ```
 
 ---
 
-### ── Source of Truth ──────────────────────────────────────────────────────────
+### ── How arr_sync.sh Keeps the Union Stable ────────────────────────────────
 
 ```bash
 # ─────────────────────────────────────────────────────────────────────────────
-# Every share has exactly one server that owns it.
+# arr_sync.sh runs as the fixed first step of intermediate_sync_maintenance.sh
-# That server's arr manages it. That server pushes it to the other via daily sync.
+# (every 4 hours). It syncs all arr libraries bidirectionally before any rsync.
-# The receiving server treats it as read-only.
 #
-# Rule: never add content to a mirrored share on the non-owning server.
+# What it does:
-# It will be overwritten on the next sync.
+#   Reads each arr's full library via the local API
+#   SSHes to the remote, reads the remote arr library via its API
+#   Adds anything missing on either side — union, not overwrite
+#   Blocked items (blocklist) are excluded from sync
+#
+# What this means in practice:
+#   No share has an owner. No server is read-only.
+#   Either server can download content to any share at any time.
+#   arr_sync.sh guarantees both arrs agree on what exists before files move.
+#   rsync then spreads the files to make storage match what arrs already know.
+#
+# arr_cleanup.sh (daily) removes true orphans — files no arr tracks.
+# arr_cleanup uses the union model too: a file is only an orphan if
+# neither arr on either server has it indexed.
 # ─────────────────────────────────────────────────────────────────────────────
 ```