fix: bincio init always sets private:true even if index.json already exists

bincio/serve/init_cmd.py

@@ -55,7 +55,19 @@ def init(data_dir: str, handle: str, password: str, display_name: str, name: str
     from datetime import datetime, timezone
 
     root_index = dd / "index.json"
-    if not root_index.exists():
+    if root_index.exists():
+        # Preserve existing manifest but always enforce private: True for a multi-user instance.
+        manifest = json.loads(root_index.read_text())
+        instance = manifest.setdefault("instance", {})
+        if not instance.get("private"):
+            instance["private"] = True
+            if name:
+                instance["name"] = name
+            root_index.write_text(json.dumps(manifest, indent=2))
+            console.print("  [green]✓[/green] root index.json updated (private: true)")
+        else:
+            console.print("  [yellow]·[/yellow] root index.json already private — skipping")
+    else:
         manifest = {
             "bas_version": "1.0",
             "instance": {"name": name or "BincioActivity", "private": True},
@@ -65,8 +77,6 @@ def init(data_dir: str, handle: str, password: str, display_name: str, name: str
         }
         root_index.write_text(json.dumps(manifest, indent=2))
         console.print("  [green]✓[/green] root index.json manifest written")
-    else:
-        console.print("  [yellow]·[/yellow] root index.json already exists — skipping")
 
     # ── User limit ────────────────────────────────────────────────────────────
     if max_users > 0: