Homepage (TDD slice 1): the status checker core

Full TDD (Q36): red test first, then the minimal implementation.
- tests/homepage_checker.bats: seam = homepage-status.py <services.json>
  <out.json>. Asserts an open port is up, a closed port is down, a wip
  service is wip (not probed), and the output carries generated_at.
- scripts/homepage-status.py: reads the config, probes each backend (tcp,
  5 s timeout), skips wip, writes status.json atomically (temp + rename).

Remaining slices: http probe method, services.json schema, the pages +
theme + toggle, the Caddyfile (validate + two hashes), the git-driven deploy.

scripts/homepage-status.py

@@ -0,0 +1,69 @@
+#!/usr/bin/env python3
+"""homepage-status.py — the homepage status checker.
+
+Reads a service config (a JSON array of service entries), probes each backend,
+and writes a status.json atomically. A wip service is not probed.
+
+Usage: homepage-status.py <services.json> <out.json>
+"""
+import json
+import os
+import socket
+import sys
+import tempfile
+from datetime import datetime, timezone
+
+TIMEOUT = 5  # seconds, per probe (Q11 / Q40)
+
+
+def probe(host, port, method="tcp"):
+    """Return 'up' if the backend answers, else 'down'."""
+    try:
+        with socket.create_connection((host, port), timeout=TIMEOUT):
+            return "up"
+    except Exception:
+        return "down"
+
+
+def main(argv):
+    if len(argv) != 3:
+        sys.stderr.write("usage: homepage-status.py <services.json> <out.json>\n")
+        return 2
+    services_path, out_path = argv[1], argv[2]
+    with open(services_path) as f:
+        services = json.load(f)
+
+    results = []
+    for svc in services:
+        if svc.get("wip"):
+            state = "wip"
+        else:
+            host, _, port = svc["probe"].rpartition(":")
+            state = probe(host, int(port), svc.get("method", "tcp"))
+        results.append({
+            "name": svc.get("name"),
+            "category": svc.get("category", "user"),
+            "state": state,
+        })
+
+    doc = {
+        "generated_at": datetime.now(timezone.utc).strftime("%Y-%m-%dT%H:%M:%SZ"),
+        "services": results,
+    }
+
+    # Atomic write: a temp file in the same directory, then rename over the target.
+    out_dir = os.path.dirname(os.path.abspath(out_path))
+    fd, tmp = tempfile.mkstemp(dir=out_dir, prefix=".status.", suffix=".tmp")
+    try:
+        with os.fdopen(fd, "w") as f:
+            json.dump(doc, f)
+        os.replace(tmp, out_path)
+    except Exception:
+        if os.path.exists(tmp):
+            os.unlink(tmp)
+        raise
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main(sys.argv))