unify single user and multi user behaviour

docs/architecture.md

@@ -96,9 +96,27 @@ index.json
 
 ## Deployment modes
 
+Single-user and multi-user share the same data layout. The only difference is whether `instance.db` exists (which enables auth).
+
+### Data layout (always)
+
+```
+{data-root}/
+  index.json        ← shard manifest (always; one shard for single-user)
+  instance.db       ← SQLite auth (only in multi-user, created by bincio init)
+  {handle}/
+    index.json      ← user's BAS feed
+    _merged/        ← sidecar-merged output
+    activities/
+    edits/
+    athlete.json
+```
+
 ### Single-user (static)
 
-No server process required. Run `bincio render`, drop `site/dist/` anywhere. The edit drawer requires `bincio edit` running locally and `PUBLIC_EDIT_URL` set in `site/.env`.
+No login, no server. Run `bincio dev --data-dir {root}` or `bincio render`, drop `site/dist/` anywhere. The site opens directly at `/u/{handle}/`. The "Feed" tab (combined feed) is hidden — there's only one user.
+
+The edit drawer requires `bincio edit` running locally and `PUBLIC_EDIT_URL` set in `site/.env`.
 
 ### Multi-user (VPS)
 
@@ -113,20 +131,7 @@ nginx / caddy
 
 `bincio serve` is a FastAPI application that owns auth, user management, and write operations. It never serves static files. nginx handles TLS and static file serving.
 
-Data is partitioned per user:
-
-```
-/data/
-  instance.db       ← SQLite: users, sessions, invites
-  index.json        ← root shard manifest (no activity data)
-  {handle}/
-    index.json      ← user's BAS feed
-    _merged/        ← sidecar-merged output
-    activities/
-    edits/
-```
-
-The root `index.json` is a shard manifest that lists user shard URLs. The browser resolves all shards concurrently and merges them into a single feed.
+The root `index.json` shard manifest lists all user shard URLs. The browser resolves them concurrently and merges activities into a combined feed at `/`.
 
 ### Instance privacy