feat: Phase 5 stabilization schedules and custodian path URIs

Add phase5_stabilization_check State Hub resolver with progress evidence
sinks, schedule projections for daily and closeout checks, custodian:// and
activity-core:// runtime path resolution, and Railiance mounts under /var/custodian.

src/activity_core/context_resolvers/state_hub.py

@@ -13,6 +13,7 @@ Supported queries:
   - daily_triage_digest: curated scalar JSON digest for daily WSJF triage
   - recently_on_scope_hourly: POST {STATE_HUB_URL}/recently-on-scope/hourly
   - consistency_sweep_remote_all: POST {STATE_HUB_URL}/consistency/sweep/remote-all
+  - phase5_stabilization_check: hub-visible Phase 5 stabilization gates
 
 No caching — state hub data is live operational state and must not be stale
 within a single workflow run.
@@ -134,9 +135,159 @@ class StateHubContextResolver(ContextResolver):
                 timeout=_SWEEP_TIMEOUT_SECONDS,
             )
             return _validate_consistency_sweep_remote_all(result)
+        if query == "phase5_stabilization_check":
+            return _phase5_stabilization_check(params)
         return {}
 
 
+def _parse_iso_datetime(raw: Any) -> datetime | None:
+    if not raw:
+        return None
+    text = str(raw).replace("Z", "+00:00")
+    try:
+        dt = datetime.fromisoformat(text)
+    except ValueError:
+        return None
+    if dt.tzinfo is None:
+        dt = dt.replace(tzinfo=timezone.utc)
+    return dt
+
+
+def _utc_now() -> datetime:
+    return datetime.now(timezone.utc)
+
+
+def _phase5_stabilization_check(params: dict[str, Any]) -> dict[str, Any]:
+    closeout = bool(params.get("closeout"))
+    now = _utc_now()
+    window_start = _parse_iso_datetime(
+        params.get("window_start", "2026-07-06T17:35:00+00:00")
+    )
+    window_end = _parse_iso_datetime(
+        params.get("window_end", "2026-07-09T17:35:00+00:00")
+    )
+    within_window = bool(
+        window_start
+        and window_end
+        and window_start <= now <= window_end
+    )
+
+    if not within_window and not closeout:
+        return {
+            "skipped": True,
+            "reason": "outside_stabilization_window",
+            "closeout": closeout,
+            "overall_pass": True,
+            "window": {
+                "start": window_start.isoformat() if window_start else None,
+                "end": window_end.isoformat() if window_end else None,
+                "within": within_window,
+            },
+            "checks": {},
+        }
+
+    baseline = params.get("baseline") or {}
+    expected_workstreams = int(baseline.get("workstreams", 640))
+    expected_tasks = int(baseline.get("tasks", 4002))
+    expected_topics = int(baseline.get("topics", 14))
+    sweep_limit = _bounded_int(params.get("sweep_limit", 6), default=6, minimum=1, maximum=24)
+    triage_max_age_hours = _bounded_int(
+        params.get("triage_max_age_hours", 36),
+        default=36,
+        minimum=1,
+        maximum=168,
+    )
+
+    health = _fetch_json("/state/health")
+    health_pass = isinstance(health, dict) and health.get("status") == "ok"
+
+    summary = _fetch_json("/state/summary")
+    totals = (summary or {}).get("totals") or {}
+    ws_total = int((totals.get("workstreams") or {}).get("total", -1))
+    task_total = int((totals.get("tasks") or {}).get("total", -1))
+    topic_total = int((totals.get("topics") or {}).get("total", -1))
+    totals_pass = (
+        ws_total == expected_workstreams
+        and task_total == expected_tasks
+        and topic_total == expected_topics
+    )
+
+    sweep_items = _fetch_json(
+        "/progress/",
+        {"event_type": "consistency_sweep_remote_all", "limit": sweep_limit},
+    )
+    sweep_rows = sweep_items if isinstance(sweep_items, list) else []
+    sweep_failures = 0
+    sweep_missing = 0
+    for item in sweep_rows:
+        detail = item.get("detail") or {}
+        if detail.get("exit_code") != 0 or detail.get("automation_error"):
+            sweep_failures += 1
+        missing = detail.get("skipped_missing") or []
+        if isinstance(missing, list) and missing:
+            sweep_missing += len(missing)
+    sweeps_pass = bool(sweep_rows) and sweep_failures == 0 and sweep_missing == 0
+
+    triage_items = _fetch_json(
+        "/progress/",
+        {"event_type": "daily_triage", "limit": 1},
+    )
+    triage_row = triage_items[0] if isinstance(triage_items, list) and triage_items else None
+    triage_at = _parse_iso_datetime(triage_row.get("created_at") if triage_row else None)
+    triage_age_hours = (
+        (now - triage_at).total_seconds() / 3600 if triage_at else None
+    )
+    triage_pass = bool(
+        triage_row
+        and triage_age_hours is not None
+        and triage_age_hours <= triage_max_age_hours
+    )
+
+    checks = {
+        "health": {"pass": health_pass, "status": health.get("status") if isinstance(health, dict) else None},
+        "totals": {
+            "pass": totals_pass,
+            "workstreams": ws_total,
+            "tasks": task_total,
+            "topics": topic_total,
+            "expected": {
+                "workstreams": expected_workstreams,
+                "tasks": expected_tasks,
+                "topics": expected_topics,
+            },
+        },
+        "sweeps": {
+            "pass": sweeps_pass,
+            "sampled": len(sweep_rows),
+            "failures": sweep_failures,
+            "missing": sweep_missing,
+        },
+        "daily_triage": {
+            "pass": triage_pass,
+            "last_at": triage_at.isoformat() if triage_at else None,
+            "age_hours": round(triage_age_hours, 2) if triage_age_hours is not None else None,
+            "max_age_hours": triage_max_age_hours,
+        },
+    }
+    overall_pass = all(section.get("pass") for section in checks.values())
+    result = {
+        "skipped": False,
+        "closeout": closeout,
+        "overall_pass": overall_pass,
+        "operator_signoff_needed": closeout and overall_pass,
+        "window": {
+            "start": window_start.isoformat() if window_start else None,
+            "end": window_end.isoformat() if window_end else None,
+            "within": within_window,
+        },
+        "checks": checks,
+        "source": str(params.get("source") or "activity-core"),
+    }
+    if closeout and not overall_pass:
+        raise RuntimeError(f"phase5 stabilization closeout failed: {result}")
+    return result
+
+
 CONTEXT_RESOLVER_REGISTRY["state-hub"] = StateHubContextResolver