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/job_queue/exec.rs

@@ -139,7 +139,7 @@ pub(super) async fn run_node(
 
 /// Boot-time forge user/token sweep as a DAG node — see
 /// [`NodeKind::ForgeSweep`]. `forge::ensure_all` already does its own
-/// per-step error handling and boot-warning banners internally (it's
+/// per-step error handling and boot warnings internally (it's
 /// best-effort by design), so this wrapper has nothing left to report;
 /// it exists purely to make the sweep a visible unit of work.
 async fn run_forge_sweep() -> Result<()> {
@@ -149,7 +149,7 @@ async fn run_forge_sweep() -> Result<()> {
 
 /// Matrix user/space sweep as a DAG node — see [`NodeKind::MatrixSweep`].
 /// Every pass reports here, whoever submitted it: as the node's own error on
-/// the dashboard, and into the debounced banner.
+/// the dashboard, and into the debounced warning.
 async fn run_matrix_sweep() -> Result<()> {
     let ok = tokio::time::timeout(MATRIX_SWEEP_DEADLINE, crate::matrix::ensure_all())
         .await
@@ -164,7 +164,7 @@ async fn run_matrix_sweep() -> Result<()> {
         health.record_ok();
         Ok(())
     } else {
-        health.record_err(matrix_sweep_banner);
+        health.record_err(matrix_sweep_warning);
         anyhow::bail!("matrix ensure_all: one or more agents failed sync (see logs)")
     }
 }
@@ -177,7 +177,7 @@ async fn run_matrix_sweep() -> Result<()> {
 /// [`Resource::MatrixSweep`]: super::resource::Resource::MatrixSweep
 const MATRIX_SWEEP_DEADLINE: std::time::Duration = std::time::Duration::from_mins(10);
 
-/// Banner for a matrix sweep that keeps failing. Two misses in a row, so one
+/// Warning for a matrix sweep that keeps failing. Two misses in a row, so one
 /// bad pass (homeserver mid-restart, a transient HTTP blip) doesn't flap the
 /// dashboard; cleared by the next clean pass.
 fn matrix_sweep_health() -> &'static Mutex<SweepHealth> {
@@ -185,7 +185,7 @@ fn matrix_sweep_health() -> &'static Mutex<SweepHealth> {
     HEALTH.get_or_init(|| Mutex::new(SweepHealth::new("matrix_ensure_all", "warn", 2)))
 }
 
-fn matrix_sweep_banner(ctx: sweep_health::SweepFailure) -> String {
+fn matrix_sweep_warning(ctx: sweep_health::SweepFailure) -> String {
     let age = ctx.since_last_ok.map_or_else(
         || "no success this session".to_owned(),
         |d| format!("last ok {} ago", sweep_health::fmt_age(d)),
@@ -200,7 +200,7 @@ fn matrix_sweep_banner(ctx: sweep_health::SweepFailure) -> String {
 
 /// `/knowledge` pull as a DAG node — see [`NodeKind::KnowledgePull`]. Every
 /// pass reports here, whoever submitted it: as the node's own error on the
-/// dashboard, and into the debounced banner.
+/// dashboard, and into the debounced warning.
 async fn run_knowledge_pull(coord: &Arc<Coordinator>) -> Result<()> {
     let result = tokio::time::timeout(
         KNOWLEDGE_PULL_DEADLINE,
@@ -242,7 +242,7 @@ async fn run_knowledge_pull(coord: &Arc<Coordinator>) -> Result<()> {
 /// [`Resource::KnowledgeTree`]: super::resource::Resource::KnowledgeTree
 const KNOWLEDGE_PULL_DEADLINE: std::time::Duration = std::time::Duration::from_mins(5);
 
-/// Banner for a `/knowledge` pull that keeps failing: three misses in a row,
+/// Warning for a `/knowledge` pull that keeps failing: three misses in a row,
 /// cleared by the next successful pull.
 fn knowledge_pull_health() -> &'static Mutex<SweepHealth> {
     static HEALTH: OnceLock<Mutex<SweepHealth>> = OnceLock::new();