docs: linux sandbox; add community interfaces JSON build script

docs/meshchatx_linux_sandbox.md

@@ -161,4 +161,4 @@ exec bwrap \
 
 ### USB serial under Bubblewrap
 
-You may need a clearer view of devices than the minimal `--dev /dev` provides. Options include `--dev-bind /dev /dev` (broader device exposure) or binding only the specific character device. Balance convenience against attack surface.
+You may need a clearer view of devices than the minimal `--dev /dev` provides. Options include `--dev-bind /dev /dev` (broader device exposure) or binding only the specific character device. Balance convenience against attack surface.

scripts/build_community_interfaces_json.py

@@ -0,0 +1,95 @@
+#!/usr/bin/env python3
+"""Emit meshchatx/src/backend/data/community_interfaces.json from the directory API or a local export."""
+# ruff: noqa: T201
+
+import argparse
+import json
+import sys
+import urllib.error
+import urllib.request
+from pathlib import Path
+
+from meshchatx.src.backend.community_interfaces_directory import (
+    DEFAULT_SUBMITTED_URL,
+    rows_from_payload,
+    transform_directory_rows,
+)
+
+ROOT = Path(__file__).resolve().parents[1]
+OUT = ROOT / "meshchatx" / "src" / "backend" / "data" / "community_interfaces.json"
+
+
+def fetch_json(url: str, timeout: float = 60.0) -> dict | list:
+    req = urllib.request.Request(
+        url,
+        headers={
+            "Accept": "application/json",
+            "User-Agent": "MeshChatX-community-interfaces-build/1.0 (+https://meshchatx.com/)",
+        },
+        method="GET",
+    )
+    with urllib.request.urlopen(req, timeout=timeout) as resp:
+        return json.loads(resp.read().decode("utf-8"))
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument(
+        "source",
+        nargs="?",
+        default=None,
+        help=f"Local JSON (directory `data` shape). Default: fetch {DEFAULT_SUBMITTED_URL}",
+    )
+    parser.add_argument(
+        "--url",
+        default=DEFAULT_SUBMITTED_URL,
+        help="Fetch URL override",
+    )
+    parser.add_argument(
+        "-o",
+        "--output",
+        type=Path,
+        default=OUT,
+        help=f"Output path (default: {OUT})",
+    )
+    args = parser.parse_args()
+
+    try:
+        if args.source:
+            payload = json.loads(Path(args.source).read_text(encoding="utf-8"))
+        else:
+            payload = fetch_json(args.url)
+    except OSError as e:
+        print(f"Read/fetch failed: {e}", file=sys.stderr)
+        return 1
+    except urllib.error.URLError as e:
+        print(f"Fetch failed: {e}", file=sys.stderr)
+        return 1
+    except json.JSONDecodeError as e:
+        print(f"Invalid JSON: {e}", file=sys.stderr)
+        return 1
+
+    try:
+        rows = rows_from_payload(payload)
+    except ValueError as e:
+        print(e, file=sys.stderr)
+        return 1
+
+    out_list = transform_directory_rows(rows)
+    doc = {
+        "_comment": "build_community_interfaces_json.py; source: directory.rns.recipes online listings. "
+        "RNode omitted. Backbone without transport_identity -> TCPClientInterface. "
+        "Optional override: public/community_interfaces.json.",
+        "_source": args.url if not args.source else str(Path(args.source).resolve()),
+        "interfaces": out_list,
+    }
+    args.output.parent.mkdir(parents=True, exist_ok=True)
+    args.output.write_text(
+        json.dumps(doc, indent=2, ensure_ascii=False) + "\n", encoding="utf-8"
+    )
+    print(f"Wrote {len(out_list)} interfaces to {args.output}")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())