dashboard: K3PT ST4T3 section + agent links open in new tab

new section between containers and questions: lists every name with a
state dir under /var/lib/hyperhive/agents/ that doesn't correspond to
a live container. shows state size + last-modified age + whether
claude creds are kept. two actions per row:

- R3V1V3 — queues a spawn approval with the same name (operator
  approves to recreate; spawn flow reuses prior config + claude
  creds, no re-login needed)
- PURG3 — wipes the agent's state + applied dirs (post /purge-tombstone/
  endpoint; refuses if a live container with that name still exists)

dashboard also opens agent links in new tabs now (target=_blank +
rel=noopener) so the operator's overview tab stays put when they
dive into an agent.

hive-c0re/src/dashboard.rs

@@ -51,6 +51,7 @@ pub async fn serve(port: u16, coord: Arc<Coordinator>) -> Result<()> {
         .route("/rebuild/{name}", post(post_rebuild))
         .route("/update-all", post(post_update_all))
         .route("/answer-question/{id}", post(post_answer_question))
+        .route("/purge-tombstone/{name}", post(post_purge_tombstone))
         .route("/request-spawn", post(post_request_spawn))
         .route("/messages/stream", get(messages_stream))
         .with_state(AppState { coord });
@@ -106,6 +107,21 @@ struct StateSnapshot {
     /// we mark the row answered and fire `HelperEvent::OperatorAnswered`
     /// into the manager's inbox.
     questions: Vec<crate::operator_questions::OpQuestion>,
+    /// State dirs (config history + claude creds + /state/ notes) that
+    /// survive after a destroy-without-purge. The operator can re-spawn
+    /// with the same name to resume, or PURG3 to wipe them.
+    tombstones: Vec<TombstoneView>,
+}
+
+#[derive(Serialize)]
+struct TombstoneView {
+    name: String,
+    /// Bytes used by the state dir tree. Cheap-ish to compute; let the
+    /// operator know how much they're holding onto.
+    state_bytes: u64,
+    /// Mtime (unix seconds) of the state dir; rough "last seen".
+    last_seen: i64,
+    has_creds: bool,
 }
 
 #[derive(Serialize)]
@@ -145,6 +161,7 @@ struct ApprovalView {
     diff_html: Option<String>,
 }
 
+#[allow(clippy::too_many_lines)]
 async fn api_state(headers: HeaderMap, State(state): State<AppState>) -> axum::Json<StateSnapshot> {
     let host = headers
         .get("host")
@@ -242,6 +259,35 @@ async fn api_state(headers: HeaderMap, State(state): State<AppState>) -> axum::J
         .unwrap_or_default();
     let questions = state.coord.questions.pending().unwrap_or_default();
 
+    // Tombstones: state-dir names that don't appear in the live container
+    // list (and aren't the manager). Operator can re-spawn or PURG3.
+    let live: std::collections::HashSet<String> = containers
+        .iter()
+        .map(|c| c.name.clone())
+        .chain(state.coord.transient_snapshot().into_keys())
+        .collect();
+    let tombstones: Vec<TombstoneView> = Coordinator::kept_state_names()
+        .into_iter()
+        .filter(|name| name != MANAGER_NAME && !live.contains(name))
+        .map(|name| {
+            let root = Coordinator::agent_state_root(&name);
+            let state_bytes = dir_size_bytes(&root);
+            let last_seen = std::fs::metadata(&root)
+                .and_then(|m| m.modified())
+                .ok()
+                .and_then(|t| t.duration_since(std::time::UNIX_EPOCH).ok())
+                .and_then(|d| i64::try_from(d.as_secs()).ok())
+                .unwrap_or(0);
+            let has_creds = claude_has_session(&Coordinator::agent_claude_dir(&name));
+            TombstoneView {
+                name,
+                state_bytes,
+                last_seen,
+                has_creds,
+            }
+        })
+        .collect();
+
     axum::Json(StateSnapshot {
         hostname,
         manager_port: MANAGER_PORT,
@@ -251,9 +297,33 @@ async fn api_state(headers: HeaderMap, State(state): State<AppState>) -> axum::J
         approvals: approval_views,
         operator_inbox,
         questions,
+        tombstones,
     })
 }
 
+/// Sum the byte size of every regular file under `root`. Cheap to compute
+/// for typical agent state (config repo + claude creds + notes file —
+/// usually a few MB); fine to do inline on each /api/state. Returns 0 on
+/// any error.
+fn dir_size_bytes(root: &Path) -> u64 {
+    fn walk(p: &Path, acc: &mut u64) {
+        let Ok(rd) = std::fs::read_dir(p) else { return };
+        for entry in rd.flatten() {
+            let Ok(ft) = entry.file_type() else { continue };
+            if ft.is_dir() {
+                walk(&entry.path(), acc);
+            } else if ft.is_file()
+                && let Ok(meta) = entry.metadata()
+            {
+                *acc += meta.len();
+            }
+        }
+    }
+    let mut total = 0u64;
+    walk(root, &mut total);
+    total
+}
+
 async fn messages_stream(
     State(state): State<AppState>,
 ) -> Sse<impl Stream<Item = Result<Event, Infallible>>> {
@@ -316,6 +386,48 @@ async fn post_answer_question(
     }
 }
 
+async fn post_purge_tombstone(
+    State(state): State<AppState>,
+    AxumPath(name): AxumPath<String>,
+) -> Response {
+    if name == lifecycle::MANAGER_NAME {
+        return error_response("refusing to purge the manager's state");
+    }
+    // Sanity: refuse to purge if a live container still exists with this
+    // name. The dashboard already filters tombstones to non-live names,
+    // but the operator could send a stale POST.
+    let live = lifecycle::list().await.unwrap_or_default();
+    if live
+        .iter()
+        .any(|c| c == &format!("{}{name}", lifecycle::AGENT_PREFIX) || c == &name)
+    {
+        return error_response(&format!(
+            "refusing to purge {name}: container still exists — use DESTR0Y first"
+        ));
+    }
+    let mut errors = Vec::new();
+    for dir in [
+        Coordinator::agent_state_root(&name),
+        Coordinator::agent_applied_dir(&name),
+    ] {
+        if dir.exists()
+            && let Err(e) = std::fs::remove_dir_all(&dir)
+        {
+            errors.push(format!("{}: {e}", dir.display()));
+        }
+    }
+    let _ = state
+        .coord
+        .approvals
+        .fail_pending_for_agent(&name, "agent state purged");
+    if errors.is_empty() {
+        tracing::info!(%name, "tombstone purged");
+        Redirect::to("/").into_response()
+    } else {
+        error_response(&format!("purge {name} partial: {}", errors.join(", ")))
+    }
+}
+
 async fn post_request_spawn(
     State(state): State<AppState>,
     Form(form): Form<RequestSpawnForm>,