deferred(2): Q4.7 plausible — drafted but 500 on cold-start, defer for operator-iterate

tests/plausible/recipe_meta.py + tests/plausible/functional/test_health_check.py drafted with
EXTRA_ENV setting required Phoenix vars (DISABLE_AUTH, DISABLE_REGISTRATION, SECRET_KEY_BASE).
Stack converges 1/1 but the served app returns HTTP 500 from / for the full 600s HTTP_TIMEOUT
window — config-class failure, not a deploy-timing issue. Diagnosing needs live container-log
inspection + iterative env tuning, more debug cycles than fit autonomous mode. Committing the
draft + a DEFERRED.md entry; operator can iterate when they want.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/plausible/functional/test_health_check.py

@@ -0,0 +1,18 @@
+"""plausible — Phase-2 health_check."""
+
+from __future__ import annotations
+
+import os
+import sys
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), "..", "..", "..", "runner"))
+from harness import http as harness_http  # noqa: E402
+
+
+def test_plausible_root_serves(live_app):
+    """GET / → 200 or 302 (redirect to login or app shell)."""
+    url = f"https://{live_app}/"
+    status, _ = harness_http.retry_http_get(
+        url, expect_status=(200, 302), max_wait=60, interval=3
+    )
+    assert status in (200, 302), f"GET {url} HTTP {status}"