feat(dash): show active model badge on agent cards (closes #2069)

Read the persisted model name from each agent's harness state file
(harness/hyperhive-model) and surface it as a small blue badge on
the container row in the SW4RM tab.

- container_view.rs: add `active_model: Option<String>` to
  ContainerView; populated by new `read_active_model` helper that
  reads harness/hyperhive-model; only set when container is running
  (stale model info from a stopped agent is misleading)
- container_view.rs: add active_model to ContainerView literal in
  host_stats test helper
- tabs.js: render badge-model chip after needs-update, before
  reminders; add active_model to the row fingerprint so re-renders
  fire on model change
- common.css: add .badge-model (blue, 80% opacity — informational)

frontend/packages/dashboard/src/common.css

@@ -85,6 +85,11 @@ code {
   color: var(--purple); border-color: var(--purple);
   text-shadow: 0 0 6px color-mix(in srgb, var(--purple) 40%, transparent);
 }
+/* Active Claude model badge on dashboard container rows. */
+.badge-model {
+  color: var(--blue); border-color: var(--blue);
+  opacity: 0.8;
+}
 /* Context-window usage badges on dashboard container rows. */
 .badge-ctx-ok {
   color: var(--green); border-color: var(--green);

frontend/packages/dashboard/src/tabs.js

@@ -521,6 +521,7 @@ window.marked = marked;
       needs_login: c.needs_login,
       needs_update: c.needs_update,
       pending_reminders: c.pending_reminders,
+      active_model: c.active_model,
       port: c.port,
       pending,
       opRunning,
@@ -726,6 +727,12 @@ window.marked = marked;
       ));
     }
 
+    if (c.active_model) {
+      head.append(el('span',
+        { class: 'badge badge-model', title: `active claude model: ${c.active_model}` },
+        c.active_model));
+    }
+
     if (c.pending_reminders && c.pending_reminders > 0) {
       head.append(el('span',
         {

hive-c0re/src/container_view.rs

@@ -44,6 +44,12 @@ pub struct ContainerView {
     /// in the tree. See `docs/agent-hierarchy.md::Current state`.
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub parent: Option<String>,
+    /// The Claude model the agent's harness is currently using, read from
+    /// `harness/hyperhive-model`. `None` when the agent has never started
+    /// a turn or the file is absent. Only meaningful when `running` is
+    /// true; the dashboard skips the badge for stopped containers.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub active_model: Option<String>,
 }
 
 /// Build the full container list. Wraps `lifecycle::list()` and
@@ -78,6 +84,14 @@ pub async fn build_all(coord: &Coordinator) -> Vec<ContainerView> {
         let needs_login = running
             && (!claude_has_session(&Coordinator::agent_claude_dir(&logical))
                 || auth_failed_sentinel(&logical));
+        // Read the active model from the harness state file. Only surfaced
+        // when the container is running — stale model info from a stopped
+        // agent is misleading (the model may change on next boot).
+        let active_model = if running {
+            read_active_model(&logical)
+        } else {
+            None
+        };
         out.push(ContainerView {
             port: lifecycle::agent_web_port(&logical),
             running,
@@ -88,6 +102,7 @@ pub async fn build_all(coord: &Coordinator) -> Vec<ContainerView> {
             deployed_sha,
             pending_reminders,
             parent,
+            active_model,
         });
     }
     out
@@ -190,6 +205,20 @@ pub async fn read_agent_status_live(name: &str) -> (Option<String>, Option<i64>,
     (text, set_at, true)
 }
 
+/// Read the active Claude model from the agent's harness state file
+/// (`harness/hyperhive-model`). Returns `None` when the file is absent
+/// or empty — callers should treat `None` as "model not yet known".
+fn read_active_model(name: &str) -> Option<String> {
+    let path = Coordinator::agent_harness_dir(name).join("hyperhive-model");
+    let s = std::fs::read_to_string(path).ok()?;
+    let trimmed = s.trim();
+    if trimmed.is_empty() {
+        None
+    } else {
+        Some(trimmed.to_owned())
+    }
+}
+
 /// Host-side hive + swarm display names, read from the c0re service's
 /// own process env. The `hive-c0re.nix` module sets these from
 /// `services.hyperhive.{hiveName, swarmName}`. The agent-side

hive-c0re/src/host_stats.rs

@@ -205,6 +205,7 @@ mod tests {
             deployed_sha: None,
             pending_reminders: 0,
             parent: None,
+            active_model: None,
         }
     }