feat(#3139): tell a container that gave up from one stopped on purpose

is_running collapsed every non-active state into false, so a container that
exhausted its bounded restarts read as plain "down" -- indistinguishable
from one an operator stopped deliberately. Bounding the restarts made that
gap sharper: a slow-failing agent used to grind on visibly, now it can stop
quietly.

Adds UnitState + unit_state() beside is_running rather than widening it.
is_running has ~8 call sites and nearly all are reconcile/power logic asking
"is it up? if not, start it" -- a question with two answers. Only the view
builder needs more, and it gets both facts from one systemctl call, since
is-active prints the state when not passed --quiet.

Surfaces as a flat failed flag on ContainerView and AgentStatusRow, matching
the shape those types already document: independent, orthogonally-observed
facts rather than a state machine. serde(default) keeps it order-independent
with the frontend half.

No behaviour change: nothing acts on the flag, per the ruling.

hive-c0re/src/container_view.rs

@@ -11,7 +11,7 @@ use std::path::Path;
 use serde::Serialize;
 
 use crate::coordinator::Coordinator;
-use crate::lifecycle::{self, AGENT_PREFIX};
+use crate::lifecycle::{self, AGENT_PREFIX, UnitState};
 
 // Independent per-agent flags, each its own badge on the dashboard card
 // and each diffed separately by `rescan_containers_and_emit`. Grouping
@@ -32,6 +32,16 @@ pub struct ContainerView {
     pub container: String,
     pub port: u16,
     pub running: bool,
+    /// The container's unit is in systemd's `failed` state — it exhausted
+    /// its bounded restarts and gave up, rather than being stopped
+    /// deliberately.
+    ///
+    /// Orthogonal to `running` rather than a variant of it: a failed unit
+    /// is not running, but a not-running unit is usually just *off*. That
+    /// distinction is the whole point — without it a container that gave
+    /// up is indistinguishable from one an operator stopped on purpose.
+    #[serde(default)]
+    pub failed: bool,
     pub needs_update: bool,
     pub needs_login: bool,
     /// First 12 chars of the sha the meta flake currently has locked
@@ -110,7 +120,12 @@ pub async fn build_all(hive: &crate::coordinator::HiveEnv) -> Vec<ContainerView>
             crate::auto_update::agent_config_pending(logical.as_str(), deployed_full).await;
         let deployed_sha = deployed_full.map(|s| s[..s.len().min(12)].to_owned());
         let parent = topology.get(logical.as_str()).cloned().flatten();
-        let running = lifecycle::is_running(logical.as_str()).await;
+        // One `systemctl` call for both facts: `unit_state` is the same
+        // shell-out `is_running` makes, minus `--quiet`. Asking twice would
+        // double the per-agent subprocess count on every SSE scan.
+        let state = lifecycle::unit_state(logical.as_str()).await;
+        let running = state == UnitState::Active;
+        let failed = state == UnitState::Failed;
         // needs_login fires when EITHER the claude session dir is missing
         // (boot-time / fresh container) OR the harness wrote the auth-failed
         // sentinel because a turn hit 401. Cleared for stopped containers —
@@ -136,6 +151,7 @@ pub async fn build_all(hive: &crate::coordinator::HiveEnv) -> Vec<ContainerView>
         out.push(ContainerView {
             port: lifecycle::agent_web_port(logical.as_str()),
             running,
+            failed,
             container: c.clone(),
             name: logical.into_string(),
             needs_update,

hive-c0re/src/lifecycle/mod.rs

@@ -530,8 +530,70 @@ async fn start_with_fallback_inner(name: &str) -> Result<()> {
         .with_context(|| format!("cold-start fallback also failed for {name}"))
 }
 
+/// The part of a container unit's systemd state we act on.
+///
+/// Deliberately not the full set: everything outside `Active`/`Failed` is
+/// one bucket, because the only distinction anything downstream makes is
+/// *gave up* versus *anything else*.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum UnitState {
+    /// Running.
+    Active,
+    /// systemd gave up on it — most often by exhausting the bounded start
+    /// limit. Its own variant precisely because it is the difference
+    /// between **gave up** and **stopped on purpose**, which every other
+    /// non-running state collapses into.
+    Failed,
+    /// `inactive` (the deliberate stop), `activating`, `deactivating`, an
+    /// unknown unit, or a `systemctl` we could not run at all.
+    Other,
+}
+
+impl UnitState {
+    /// Parse `systemctl is-active`'s stdout.
+    ///
+    /// Split out from the shell-out so the mapping is testable without a
+    /// systemd to ask — the states we care about are the two we name, and
+    /// everything else must land in `Other` rather than being guessed at.
+    fn from_is_active(stdout: &str) -> Self {
+        match stdout.trim() {
+            "active" => Self::Active,
+            "failed" => Self::Failed,
+            _ => Self::Other,
+        }
+    }
+}
+
+/// The container unit's state, in one `systemctl` call.
+///
+/// `is-active` **prints** the state and exits 0 only for `active`, so
+/// dropping `--quiet` yields both facts from the call [`is_running`]
+/// already makes. That matters: the status path runs this per agent (see
+/// the spawn-count note in `socket_server::lifecycle_handlers`), so a
+/// caller wanting *running* and *failed* must not pay for two subprocesses.
+pub async fn unit_state(name: &str) -> UnitState {
+    let container = container_name(name);
+    let unit = format!("container@{container}.service");
+    match Command::new("systemctl")
+        .args(["is-active", &unit])
+        .output()
+        .await
+    {
+        Ok(out) => UnitState::from_is_active(&String::from_utf8_lossy(&out.stdout)),
+        // Not "the unit is fine" and not "the unit failed" — we simply do
+        // not know, and saying `Failed` here would report a gave-up agent
+        // every time `systemctl` itself was unavailable.
+        Err(_) => UnitState::Other,
+    }
+}
+
 /// True when the container's systemd unit is active. Used by the dashboard
 /// to gate stop/restart buttons.
+///
+/// Kept boolean on purpose: nearly every caller is reconcile/power logic
+/// asking "is it up? if not, start it", and that question has two answers.
+/// A caller that needs to tell *failed* from *stopped* wants
+/// [`unit_state`] instead.
 pub async fn is_running(name: &str) -> bool {
     let container = container_name(name);
     let unit = format!("container@{container}.service");

hive-c0re/src/lifecycle/tests.rs

@@ -180,3 +180,42 @@ async fn update_ref_cas_refuses_stale_expectation() {
         "ref moved even though the CAS failed"
     );
 }
+
+/// `systemctl is-active` prints the state with a trailing newline, which is
+/// the whole reason this parser trims rather than comparing raw.
+#[test]
+fn unit_state_reads_what_is_active_prints() {
+    assert_eq!(UnitState::from_is_active("active\n"), UnitState::Active);
+    assert_eq!(UnitState::from_is_active("failed\n"), UnitState::Failed);
+    assert_eq!(UnitState::from_is_active("inactive\n"), UnitState::Other);
+    // No trailing newline, in case the capture ever changes shape.
+    assert_eq!(UnitState::from_is_active("failed"), UnitState::Failed);
+}
+
+/// The asymmetry that matters: an unrecognised state must fall to `Other`,
+/// never to `Failed`.
+///
+/// `Failed` is what the dashboard will render as *this agent gave up*, so a
+/// wrong `Failed` invents an incident, while a wrong `Other` merely fails to
+/// distinguish one from a deliberate stop — the behaviour we have today.
+/// Guessing in the safe direction is the property, not an implementation
+/// detail of the `match`.
+#[test]
+fn an_unknown_state_is_never_reported_as_failed() {
+    for s in [
+        "activating",
+        "deactivating",
+        "reloading",
+        "maintenance",
+        "unknown",
+        "",
+        "Failed",  // capitalised: systemd prints lowercase, so this is not a state
+        "failed*", // `is-active` never emits this; a substring match would take it
+    ] {
+        assert_eq!(
+            UnitState::from_is_active(s),
+            UnitState::Other,
+            "{s:?} must not be read as a give-up"
+        );
+    }
+}

hive-c0re/src/server.rs

@@ -357,6 +357,7 @@ async fn handle_agent_status(coord: &Arc<Coordinator>) -> HostResponse {
         .map(|v| hive_sh4re::container::AgentStatusRow {
             name: v.name,
             running: v.running,
+            failed: v.failed,
             needs_update: v.needs_update,
             needs_login: v.needs_login,
             deployed_sha: v.deployed_sha,

hive-c0re/src/stats/host_stats.rs

@@ -248,6 +248,7 @@ mod tests {
             container: format!("h-{name}"),
             port: 0,
             running: true,
+            failed: false,
             needs_update: false,
             needs_login,
             deployed_sha: None,