feat(monitors): problems first, a page per monitor, adding on its own page (#5121)

The Monitors list now opens with a count strip (down, up with how many
degraded, pending, paused) and sorts down, degraded, pending, up, paused,
by name within each. Degraded is up but worth a look: uptime at or below
its warning floor, or the latest response past its critical cutoff, both
from Settings → Thresholds; a slow-but-tolerable reply is coloured, not
sorted.

A monitor had no page of its own: every link went to the list. Now
/monitors/<id> shows its state and since when, latency, uptime for 24h/7d/
30d, TLS days, the last checks, recent failures with their errors, and its
settings (HTTP header names, never their values). Status links to it, and
adding or editing returns to it.

Adding is its own page (/monitors/new, form.html shared with edit) behind
an "Add monitor" button; a refused add re-renders the form with the error
and what was typed instead of a bare 400 text. Row actions are labelled
icon buttons, type names read Ping/TCP/DNS/HTTP (|monitor_type), and the
heartbeat uses pill-up/pill-down, so HEX_CEILING drops to 56.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

steward/monitors/routes.py

@@ -15,7 +15,9 @@ from steward.core import renames
 from steward.core.audit import audit_request
 from steward.models.users import UserRole
 from steward.models.monitors import Monitor, MonitorType, MONITOR_TYPE_VALUES
+from steward.core.status import _heartbeat_title, streak_start
 from steward.core.time_range import DEFAULT_RANGE
+from steward.models.hosts import Host
 from steward.monitors import service as monitor_svc
 
 monitors_bp = Blueprint("monitors", __name__, url_prefix="/monitors")
@@ -49,7 +51,6 @@ async def index():
         "monitors/index.html",
         poll_interval=poll_interval,
         current_range=request.args.get("range", DEFAULT_RANGE),
-        types=list(MonitorType),
     )
 
 
@@ -57,11 +58,11 @@ async def index():
 @require_role(UserRole.viewer)
 async def rows():
     async with current_app.db_sessionmaker() as db:
-        data, up, down, pending, range_key = await monitor_svc.monitor_rows(
-            db, request.args.get("range", DEFAULT_RANGE))
+        data, counts, range_key = await monitor_svc.monitor_rows(
+            db, request.args.get("range", DEFAULT_RANGE), current_app.config.get("THRESHOLDS", {}))
     return await render_template(
         "monitors/rows.html",
-        monitor_data=data, up=up, down=down, pending=pending, range_key=range_key,
+        monitor_data=data, counts=counts, range_key=range_key,
     )
 
 
@@ -76,7 +77,7 @@ async def add_monitor():
             check_interval_seconds=form.get("check_interval_seconds"),
             opts=_form_opts(form, mtype))
     except ValueError as exc:
-        return str(exc), 400
+        return await _new_form(form, mtype, str(exc)), 400
 
     host_id = form.get("host_id", "").strip() or None
     monitor = Monitor(id=str(uuid.uuid4()), host_id=host_id, enabled=True,
@@ -86,13 +87,58 @@ async def add_monitor():
             try:
                 await monitor_svc.check_name_free(db, monitor.type, monitor.name)
             except ValueError as exc:
-                return str(exc), 400
+                return await _new_form(form, mtype, str(exc)), 400
             db.add(monitor)
 
-    # A host-scoped add returns to that host's hub; otherwise the monitors page.
+    # A host-scoped add returns to that host's hub; otherwise the new monitor's page.
     if host_id:
         return redirect(url_for("hosts.host_detail", host_id=host_id))
-    return redirect(url_for("monitors.index"))
+    return redirect(url_for("monitors.detail", monitor_id=monitor.id))
+
+
+async def _new_form(form, mtype: str, error: str | None = None) -> str:
+    """The add form, holding what was typed when `error` sends it back."""
+    values = {k: form.get(k, "") for k in ("name", "target", "host_id")}
+    values["check_interval_seconds"] = form.get("check_interval_seconds", 0)
+    return await render_template(
+        "monitors/form.html", monitor=None, values=values,
+        mtype=mtype if mtype in MONITOR_TYPE_VALUES else MonitorType.icmp.value,
+        config=_form_opts(form, mtype) if error and mtype in MONITOR_TYPE_VALUES else {},
+        types=list(MonitorType), error=error,
+    )
+
+
+@monitors_bp.get("/new")
+@require_role(UserRole.operator)
+async def new_form():
+    return await _new_form({"host_id": request.args.get("host_id", "")}, MonitorType.icmp.value)
+
+
+@monitors_bp.get("/<monitor_id>")
+@require_role(UserRole.viewer)
+async def detail(monitor_id: str):
+    async with current_app.db_sessionmaker() as db:
+        m = await db.get(Monitor, monitor_id)
+        if not m:
+            return redirect(url_for("monitors.index"))
+        st = (await monitor_svc.monitor_states(db, [m]))[m.id]
+        failures = await monitor_svc.recent_failures(db, m.id)
+        host = await db.get(Host, m.host_id) if m.host_id else None
+    thresholds = current_app.config.get("THRESHOLDS", {})
+    latest = st["latest"]
+    since, since_at_least = streak_start(st["recent"])
+    if st["down_since"]:
+        since, since_at_least = st["down_since"], False
+    tls_days = None
+    if latest and latest.tls_expires_at:
+        tls_days = (latest.tls_expires_at - datetime.now(timezone.utc)).total_seconds() / 86400.0
+    return await render_template(
+        "monitors/detail.html", monitor=m, host=host, latest=latest, failures=failures,
+        state=monitor_svc.row_state(m, latest, st["uptime"].get("24h"), thresholds),
+        since=since, since_at_least=since_at_least, uptime=st["uptime"], tls_days=tls_days,
+        heartbeat=[{"state": "up" if r.is_up else "down", "title": _heartbeat_title(m.type, r)}
+                   for r in st["recent"]],
+    )
 
 
 @monitors_bp.get("/<monitor_id>/edit")
@@ -103,7 +149,8 @@ async def edit_form(monitor_id: str):
     if not m:
         return redirect(url_for("monitors.index"))
     return await render_template(
-        "monitors/edit.html", monitor=m, config=m.config, types=list(MonitorType),
+        "monitors/form.html", monitor=m, values=None, mtype=m.type, config=m.config,
+        types=list(MonitorType), error=None,
     )
 
 
@@ -135,7 +182,7 @@ async def edit_monitor(monitor_id: str):
     if moved:
         await audit_request("monitor.updated", "monitor", m.name,
                             {"monitor_id": m.id, "renamed_from": old_name, "carried": moved})
-    return redirect(url_for("monitors.index"))
+    return redirect(url_for("monitors.detail", monitor_id=m.id))
 
 
 @monitors_bp.post("/<monitor_id>/toggle")
@@ -157,7 +204,10 @@ async def delete_monitor(monitor_id: str):
             m = await db.get(Monitor, monitor_id)
             if m:
                 await db.delete(m)
-    return redirect(request.referrer or url_for("monitors.index"))
+    referrer = request.referrer or ""
+    if f"/monitors/{monitor_id}" in referrer:
+        return redirect(url_for("monitors.index"))
+    return redirect(referrer or url_for("monitors.index"))
 
 
 @monitors_bp.get("/widget")
@@ -169,7 +219,9 @@ async def widget():
     widget_id = request.args.get("wid", "0")
 
     async with current_app.db_sessionmaker() as db:
-        data, up, down, pending, _ = await monitor_svc.monitor_rows(db, DEFAULT_RANGE)
+        data, counts, _ = await monitor_svc.monitor_rows(
+            db, DEFAULT_RANGE, current_app.config.get("THRESHOLDS", {}))
+    up, down, pending = counts["up"], counts["down"], counts["pending"]
     if type_filter in MONITOR_TYPE_VALUES:
         data = [d for d in data if d["monitor"].type == type_filter]
     if show_down_only: