hive-c0re: hive warnings reach the operator as metrics and alerts, not a banner

The dashboard's top-of-page warning banner is gone. The warning registry
stays, because /health/ready, the swarm status view and the OTEL gauges
read it. What it feeds is now alerted on in Grafana:

- hyperhive.hive.warning{kind,level}: one series per raised warning, so an
  alert names the cause. Raising a warning also logs one `hive warning
  raised` line with the message.
- hyperhive.hive.nix_store.utilization: the used fraction of the nix
  store's filesystem, probed in the gauge callback.
- Alerts: hh-hive-degraded on the existing degraded gauge, hh-hive-warning
  per kind (disk excluded), hh-host-disk-high at 85% and
  hh-host-disk-critical at 95%.
- pending_logins is now a registry warning, refreshed from the container
  rescan, so it reaches the per-kind gauge.

Frontend: server_warnings leaves the state snapshot, and the dashboard,
flow and stats pages keep only the sticky chrome wrapper. The shared
hive-warn and WarnBanner components stay, since other views use them.

A module-eval case checks each alert's metric name against the exporter's
source, so a rename on either side fails the build.

frontend/packages/dashboard/src/common.css

@@ -564,7 +564,7 @@ hive-side-panel .md td {
    Inverted-gutter layout: the dashboard keeps `<body>` full-bleed
    and wraps their padded content in a single `.page-content` div that
    carries the horizontal gutter. Full-width chrome (the tab strip, the
-   server-warnings banner, the footer) then spans edge-to-edge for free,
+   footer) then spans edge-to-edge for free,
    with no negative-margin breakout hacks. Only matches on pages that opt
    in by adding the wrapper (index.html); FL0W / ST4TS
    are full-bleed with their own `.<page>-main` padding. */
@@ -573,50 +573,14 @@ hive-side-panel .md td {
 }
 
 /* ─── sticky top region ───────────────────────────────────────────────
-   One sticky container per page holding the warning banner above the
-   page chrome (tab bar / page header). common.js (ensureStickyTop)
-   wraps the page's chrome in this on first render and injects the banner
-   as its first child, so the banner + chrome stack in a single sticky
-   context — pinned together — instead of two separate `top:0` stickies
-   colliding (the banner used to overlay the tab bar). */
+   One sticky container per page holding the page chrome (tab bar / page
+   header). common.js (initStickyTop) wraps the chrome in this on load. */
 .sticky-top {
   position: sticky;
   top: 0;
   z-index: 50;
 }
 
-/* ─── server warnings banner ──────────────────────────────────────────
-   Generic top-of-page strip, injected as the first child of `.sticky-top`
-   by common.js (renderServerWarnings) on every page. One row per warning;
-   colour comes from the per-warning `level` (warn = amber, crit = red).
-   Stickiness lives on the `.sticky-top` wrapper, not here. The bar spans
-   the full width edge-to-edge; the dashboard is full-bleed at the
-   body level (their 1.5em gutter lives on an inner `.page-content`
-   wrapper), so the banner is full-width for free. */
-.server-warnings[hidden] {
-  display: none;
-}
-.server-warn {
-  text-align: center;
-  padding: 0.4em 1em;
-  font-size: 0.85em;
-  font-weight: bold;
-  letter-spacing: 0.02em;
-}
-/* Tint composited over the opaque elevated-surface grey (not transparent):
-   the bar is `position: sticky`, so a see-through background would let
-   page content scroll through behind it. */
-.server-warn-warn {
-  color: var(--amber);
-  background: color-mix(in srgb, var(--amber) 16%, var(--bg-elev));
-  border-bottom: 1px solid var(--amber);
-}
-.server-warn-crit {
-  color: var(--red);
-  background: color-mix(in srgb, var(--red) 18%, var(--bg-elev));
-  border-bottom: 1px solid var(--red);
-}
-
 /* ─── stats table ─────────────────────────────────────────────────
    Shared right-aligned numeric table. Used by /stats.html (busiest
    agents) — moved here from dashboard.css when ST4TS became its own

frontend/packages/dashboard/src/common.js

@@ -562,22 +562,12 @@ export function appendLinkified(parent, text, refs) {
   }
 }
 
-// ─── server warnings banner ──────────────────────────────────────────
-// A generic top-of-page banner shown on every page (dashboard + the
-// stand-alone FL0W / ST4TS pages). The backend decides what to
-// warn about — `/api/state.server_warnings` is a list of
-// `{ kind, level, message }` — and this just renders it, coloured by
-// `level` (`warn` amber / `crit` red). Adding a new system warning is a
-// backend-only change. The bar is injected at the top of <body> so no
-// page needs to add markup.
-
-// The sticky top region — one sticky container holding the warning
-// banner above the page's chrome (tab bar / page header), so the banner
-// stacks with the chrome instead of being overlaid by it (two separate
-// `top:0` stickies would otherwise collide). Built once by wrapping the
-// page's existing chrome element; pages without a chrome (none today)
-// get a banner-only sticky region at the top of <body>.
-function ensureStickyTop() {
+// ─── sticky top region ───────────────────────────────────────────────
+// One sticky container wrapping the page's chrome (tab bar / page
+// header), built once by wrapping the existing chrome element. A page
+// without a chrome (none today) gets an empty sticky region at the top of
+// <body>.
+export function initStickyTop() {
   let top = document.querySelector(".sticky-top");
   if (top) return top;
   top = document.createElement("div");
@@ -591,51 +581,3 @@ function ensureStickyTop() {
   }
   return top;
 }
-
-function ensureServerWarningsBar() {
-  let bar = document.getElementById("server-warnings");
-  if (!bar) {
-    bar = document.createElement("div");
-    bar.id = "server-warnings";
-    bar.className = "server-warnings";
-    bar.setAttribute("role", "alert");
-    bar.hidden = true;
-    ensureStickyTop().prepend(bar);
-  }
-  return bar;
-}
-
-/// Render a `server_warnings` list (from /api/state) into the banner.
-/// Empty / missing → the bar hides itself.
-export function renderServerWarnings(warnings) {
-  const bar = ensureServerWarningsBar();
-  bar.replaceChildren();
-  if (!Array.isArray(warnings) || warnings.length === 0) {
-    bar.hidden = true;
-    return;
-  }
-  for (const w of warnings) {
-    const row = el("div", {
-      class:
-        "server-warn server-warn-" +
-        (w && w.level === "crit" ? "crit" : "warn"),
-    });
-    appendText(row, "⚠ " + ((w && w.message) || ""));
-    bar.append(row);
-  }
-  bar.hidden = false;
-}
-
-/// One-shot init for pages that don't otherwise poll /api/state: ensure
-/// the bar exists, fetch the snapshot once, render. The dashboard (which
-/// already polls /api/state) calls `renderServerWarnings` directly for
-/// live updates instead.
-export function initServerWarnings() {
-  ensureServerWarningsBar();
-  fetch("/api/state")
-    .then((r) => (r.ok ? r.json() : null))
-    .then((s) => renderServerWarnings(s && s.server_warnings))
-    .catch(() => {
-      /* non-fatal: no banner if the snapshot is unreachable */
-    });
-}

frontend/packages/dashboard/src/dashboard.css

@@ -17,7 +17,7 @@
 body.dashboard-shell {
   /* Full-bleed body (no horizontal gutter). The 1.5em side gutter lives
      on the inner `.page-content` wrapper (see common.css), so the sticky
-     chrome bar, the server-warnings banner, and the footer span the full
+     chrome bar and the footer span the full
      width edge-to-edge with no negative-margin breakout. `padding-bottom`
      keeps a little breathing room above the viewport edge (overridden to
      clear the selection bar via `.has-selection` below). No max-width cap
@@ -34,8 +34,7 @@ body.dashboard-shell {
   align-items: center;
   gap: 0.75em;
   /* Stickiness lives on the `.sticky-top` wrapper (common.css) that
-     common.js wraps this chrome in, alongside the server-warning banner,
-     so they stack in one sticky context instead of colliding. */
+     common.js wraps this chrome in. */
   background: color-mix(in srgb, var(--bg) 86%, transparent);
   -webkit-backdrop-filter: blur(8px) saturate(120%);
   backdrop-filter: blur(8px) saturate(120%);

frontend/packages/dashboard/src/flow.js

@@ -10,17 +10,12 @@
 // container list).
 
 import { create as termCreate } from "@hive/shared/terminal.js";
-import {
-  $,
-  appendLinkified,
-  openStream,
-  initServerWarnings,
-} from "./common.js";
+import { $, appendLinkified, openStream, initStickyTop } from "./common.js";
 import { el } from "@hive/shared/dom.js";
 import { epochSec } from "./util.js";
 
 (() => {
-  initServerWarnings();
+  initStickyTop();
 
   // ─── local containers cache (for compose autocomplete) ──────────────────
   // The compose box's @-mention completion suggests known agent names.

frontend/packages/dashboard/src/stats.js

@@ -5,7 +5,7 @@
 // this bundle has no chart lib; per-agent trend charts live on each
 // agent's own /stats page. The window selector is a hash-routed
 // createTabStrip (#1h / #24h / …), matching the per-agent stats page.
-import { $, initServerWarnings } from "./common.js";
+import { $, initStickyTop } from "./common.js";
 import { createTabStrip } from "@hive/shared/tabs.js";
 
 let hiveStatsWindow = "24h";
@@ -173,7 +173,7 @@ async function refreshHiveStats() {
   }
 }
 
-initServerWarnings();
+initStickyTop();
 
 // Window selector → hash-routed createTabStrip (#1h / #24h / …). No panes
 // here (the selector swaps data, not DOM); paneFor() returns null for each

frontend/packages/dashboard/src/tabs.js

@@ -11,7 +11,7 @@
 // 4G3NTS (containers) domain lives in `./agents.js`.
 
 import { marked } from "marked";
-import { $, openStream, renderServerWarnings } from "./common.js";
+import { $, openStream, initStickyTop } from "./common.js";
 import { el } from "@hive/shared/dom.js";
 import { bindAsyncForms } from "@hive/shared/forms.js";
 import { createTabStrip } from "@hive/shared/tabs.js";
@@ -50,6 +50,8 @@ import { renderLinksMenu } from "./links-menu.js";
 window.marked = marked;
 
 (() => {
+  initStickyTop();
+
   // ─── async forms ────────────────────────────────────────────────────────
   // Shared `data-async` submit interceptor (in common.js, shared with the other
   // pages' bundles). On success it re-runs refreshState unless the form
@@ -135,7 +137,6 @@ window.marked = marked;
       // synchronous read (e.g. the compose autocomplete pulls agent
       // names from here instead of refetching on every keystroke).
       window.__hyperhive_state = s;
-      renderServerWarnings(s.server_warnings);
       // Hive identity: render the swarm/hive name as a headline at the
       // top of the 4G3NTS pane + update the page title once the
       // server-side display names are known. `hive_name` / `swarm_name`