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.

hive-c0re/src/workers/crash_watch.rs

@@ -149,7 +149,7 @@ fn emit_crash_transitions(coord: &Coordinator, prev: &HashSet<String>, current:
         // The one place this fires: a swarm-level grafana alert
         // (`hh-container-crashed` in `nix/host-modules/swarm-grafana.nix`)
         // matches this exact message against the log store and pages the
-        // operator directly — no agent (and no per-hive dashboard banner)
+        // operator directly — no agent (and no per-hive warning)
         // in the loop. See `docs/scheduler/observability.md`.
         tracing::warn!(agent = %stopped, "container crash detected");
     }

hive-c0re/src/workers/permissions_import.rs

@@ -181,7 +181,7 @@ impl ImportOutcome {
         matches!(self, Self::NothingPending | Self::Imported)
     }
 
-    /// Why reading is not allowed, for the caller's log and banner.
+    /// Why reading is not allowed, for the caller's log and warning.
     #[must_use]
     pub fn into_error(self) -> Option<anyhow::Error> {
         match self {

hive-c0re/src/workers/swarm_limits.rs

@@ -24,11 +24,11 @@ use crate::stats::sweep_health::{self, SweepHealth};
 pub const READ_INTERVAL: Duration = Duration::from_secs(30);
 
 /// At [`READ_INTERVAL`] this is ~90 seconds of failing reads.
-const FAILURES_BEFORE_BANNER: u32 = 3;
+const FAILURES_BEFORE_WARNING: u32 = 3;
 
 /// Read the caps now and every [`READ_INTERVAL`] until shutdown.
 pub async fn follow(client: async_nats::Client, mut shutdown: tokio::sync::watch::Receiver<bool>) {
-    let mut health = SweepHealth::new("swarm_limits_read", "warn", FAILURES_BEFORE_BANNER);
+    let mut health = SweepHealth::new("swarm_limits_read", "warn", FAILURES_BEFORE_WARNING);
     loop {
         match sync(&client).await {
             Ok(()) => health.record_ok(),

hive-c0re/src/workers/swarm_permissions.rs

@@ -30,7 +30,7 @@ use crate::stats::sweep_health::{self, SweepHealth};
 pub const READ_INTERVAL: Duration = Duration::from_secs(30);
 
 /// At [`READ_INTERVAL`] this is ~90 seconds of failing reads.
-const FAILURES_BEFORE_BANNER: u32 = 3;
+const FAILURES_BEFORE_WARNING: u32 = 3;
 
 /// Send the meta repo's grants once, then read the permissions now and every
 /// [`READ_INTERVAL`] until shutdown.
@@ -40,7 +40,7 @@ pub async fn follow(
     hive: String,
     mut shutdown: tokio::sync::watch::Receiver<bool>,
 ) {
-    let mut health = SweepHealth::new("swarm_permissions_read", "warn", FAILURES_BEFORE_BANNER);
+    let mut health = SweepHealth::new("swarm_permissions_read", "warn", FAILURES_BEFORE_WARNING);
     loop {
         let import = super::permissions_import::send_pending(&client, &hive).await;
         let pass = if import.read_allowed() {

hive-c0re/src/workers/wanted.rs

@@ -76,7 +76,7 @@ pub async fn pull(coord: &Arc<Coordinator>) -> Result<()> {
     let client =
         match tokio::time::timeout_at(deadline, crate::swarm_queue::wait_for_client()).await {
             // Absent — already reported by the shared connector (an `info` log or
-            // a `swarm_queue_config` banner).
+            // a `swarm_queue_config` warning).
             Ok(None) => return Ok(()),
             Ok(Some(client)) => client,
             Err(_) => anyhow::bail!("no swarm queue client within {}s", CONNECT_WAIT.as_secs()),